Introduction to Marine Conservation Biology

Home , Conservation biology, Green moray, Hydrobiology, Island Press, Marine conservation, Marine habitats

Network of Conservation Educators & Practitioners

Author(s): Tundi Agardy

Source: Lessons in Conservation, Vol. 1, pp. 5-43

Published by: Network of Conservation Educators and Practitioners, Center for Biodiversity and Conservation, American Museum of Natural History

Stable URL: ncep.amnh.org/linc/

This article is featured in Lessons in Conservation, the oﬀicial journal of the Network of Conservation Educators and Practitioners (NCEP). NCEP is a collaborative project of the American Museum of Natural History’s Center for Biodiversity and Conservation (CBC) and a number of institutions and individuals around the world. Lessons in Conservation is designed to introduce NCEP teaching and learning resources (or “modules”) to a broad audience. NCEP modules are designed for undergraduate and professional level education. These modules—and many more on a variety of conservation topics—are available for free download at our website, ncep.amnh.org.

To learn more about NCEP, visit our website: ncep.amnh.org.

All reproduction or distribution must provide full citation of the original work and provide a copyright notice as follows:

Illustrations obtained from the American Museum of Natural History’s library: images.library.amnh.org/digital/ SYNTHESIS Introduction to Marine Conservation Biology

Tundi Agardy*

*Sound Seas, Bethesda, MD, USA, email [email protected] D. Brumbaugh

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS

Table of Contents

Introduction...... 7 Marine and Coastal Systems...... 7 Key Concepts in Marine Conservation Biology...... 7 Comparisons Between Marine and Terrestrial Systems...... 9 Marine Organisms and Environments...... 10 Marine Biodiversity...... 10 Habitat Diversity...... 10 Phyletic and Species Diversity...... 10 Genetic Diversity...... 10 Physical Oceanography...... 11 Physical Environment at Various Scales...... 11 Macro Scale Oceanography...... 11 Meso Scale Oceanography...... 11 Micro Scale Oceanography...... 12 Links Between Physical Oceanography and Biota...... 12 Major Marine Ecosystems...... 13 Nearshore Ecosystems...... 13 Kelp Forests and Hard Bottoms...... 13 Estuaries and Tidal Wetlands Such as Mangroves...... 14 Soft Sediments and Sea Mounts...... 15 Coral Reefs...... 16 Seagrass Beds...... 16 Offshore Open Water...... 18 Marine Ecology...... 19 Marine Population Ecology...... 19 Life History...... 19 Reproduction...... 20 Larval Ecology and Recruitment...... 20 Community Ecology...... 21 Marine Resource Use and Conservation...... 23 Marine Resource Use...... 23 Threats To Marine Ecosystems and Biodiversity...... 24 General...... 24 Habitat Loss and Degradation...... 25 Resource Extraction...... 26 Invasive Species (Including Pathogenic Diseases)...... 26 Climate Change...... 27 Most Threatened Areas...... 27 Methods to Conserve Marine Biodiversity...... 28 Spatial Management Through Zoning and Marine Protected Areas ...... 28 Fisheries Management...... 29 Restoration...... 30 Integrated Coastal Zone Management...... 31 Regional and International Agreements/Treaties...... 31 Constraints to Effective Marine Conservation...... 32 Conclusions...... 34 Terms of Use...... 34 Literature Cited...... 35 Glossary...... 40

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS

Introduction to Marine Conservation Biology Tundi Agardy

This document is specifically about those aspects of marine nificantly to global biological diversity. biology that are used in marine conservation. It is not intend- ed to be a complete primer on marine conservation, which Marine and coastal systems play significant roles in the eco- incorporates other sciences (most notably the social sciences) logical processes that support life on earth and contribute as well as traditional knowledge. To learn more about other to human well-being. These include climate regulation, the aspects of marine conservation, please refer to the following freshwater cycle, food provisioning, biodiversity mainte- marine modules: Marine Conservation Policy, Marine Protected nance, and energy and cultural services including recreation Areas and MPA Networks, and International Treaties for Marine and tourism. They are also an important source of economic Conservation and Management, all of which complement this growth. Capture fisheries alone were worth approximately module. 81 billion USD in 2000 (FAO, 2002), while aquaculture net- ted 57 billion USD in 2000 (FAO, 2002). In 1995, offshore Introduction gas and oil was worth 132 billion USD, while marine tourism brought in 161 billion USD, and trade and shipping were Marine and Coastal Systems worth 155 billion USD (McGinn, 1999). There are currently approximately 15 million fishers employed aboard fishing Almost three-quarters of the Earth’s surface (exactly 70.8% of vessels in the marine capture fisheries sector, the vast majority the total surface area or 362 million km2), is covered by oceans on small boats (90% of fishers work on vessels less than 24 m and major seas. Within these marine areas are ecosystems that in length) (MA, 2005c). are fundamental to life on earth and are among the world’s most productive, yet threatened, natural systems. Continental Key Concepts in Marine Conservation Biology shelves and associated Large Marine Ecosystems (LMEs) provide many key ecosystem services: shelves account for at least Marine ecosystems are complex and exhibit diversity at vari- 25% of global primary productivity, 90-95% of the world’s ous hierarchical levels. Of 32 common phyla on the earth, only marine fish catch, 80% of global carbonate production, 50% one living phylum is strictly terrestrial; all others have marine of global denitrification, and 90% of global sedimentary min- representatives (Norse, 1993). Interestingly, all of these phyla eralization (UNEP, 1992). had differentiated by the dawn of the Cambrian, almost 600 million years ago, and all evolved in the sea. Since that time Marine systems are highly dynamic and tightly connected the sea has been frozen, experienced extensive anaerobic con- through a network of surface and deep currents. In marine ditions, been blasted by meteorites, and undergone substantial systems, the properties of the watery medium generate densi- sea level variation. The sea has thus been fragmented and ty layers, thermoclines, and gradients of light penetration. These coalesced, resulting in a vast array of habitats (MA, 2005a). phenomena give the systems vertical structure, which results in vertically variable productivity. Tides, currents, and upwell- Marine species are poorly known relative to those on land. ings break this stratification and, by forcing the mixing of water The actual species diversity in the ocean is not known, and layers, enhance production (MA, 2005c). Coastal systems also fewer than 300,000 of the estimated 10 million species have exhibit a wide variety of habitats that in turn contribute sig- been described (MA, 2005a). One of the rare efforts to sample

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS

all of the mollusk species at a tropical site found 2,738 species (one upper and one lower) are passed, the phase shift occurs of marine mollusks in a limited area near New Caledonia suddenly (within months). The resulting ecosystem, though (Bouchet et al., 2002). stable, is less productive and less diverse. Human well being is affected not only by reductions in food supply and decreased Natural systems in the sea, income from reef-related as on land, exhibit non-lin- industries (e.g., diving and ear dynamics. Thresholds snorkeling, aquarium fish for responses to perturba- collecting, etc.), but also tion occur in some systems, by increased costs accruing though few have actually from the decreased ability been identified. Significant of reefs to protect shore- alteration in ecosystem lines. Algal reefs, for exam- structure and function can ple, are more prone to being occur when certain trig- broken up in storm events, gers result in changes in the leading to shoreline erosion dominant species. Regime and seawater breaches of shifts are common in pelagic land. Such phase shifts have fisheries, where thresholds been documented in Jamai- are surmised to be related to ca, elsewhere in the Carib- temperatures (IPCC, 2003). bean, and in Indo-Pacific Most well known is the ex- reefs (MA, 2005b). ample of the anchovy/sar- dine regime shift, which is Introduced alien species (or expressed as a periodic os- invasive species) can also cillation between dominant act as a trigger for dramatic species, not an irreversible changes in ecosystem struc- change. Irreversible shifts ture, function, and delivery occur when a system fails to Pillar coral, Dendrogyra cylindrus, and juvenile bluehead wrasse of services. In the marine off of the coast of Andros Island (Source: D. Brumbaugh) return to its former state in environment, species are time scales of multiple hu- commonly brought into man generations, after driving forces leading to change are new areas through ballast water discharges, and can quickly reduced or removed (IPCC, 2003). gain a foothold as they outcompete native species for food and space. A prime example of a sudden, and irreversible, Some phase shifts are essentially irreversible, such as the coral change in an ecosystem occurred in the Black Sea. Introduc- reef ecosystems that undergo rather sudden shifts from coral- tion of the carnivorous ctenophore Mnemiopsis leidyi caused the dominated to algal-dominated reefs (Birkeland, 2004). The loss of 26 major fisheries species, and has been implicated trigger for such changes is usually multi-faceted, and includes (along with other factors) in subsequent growth of the anoxic increased nutrient input. This leads to eutrophied conditions “dead zone” (Zaitsev and Mamaev, 1997). Introduced species and removal of the herbivorous fishes that maintain the bal- arrive via other vectors as well, such as through the disposal ance between corals and algae. Once the thresholds for the of packing materials for marine resources, and are not always two ecological processes of nutrient loading and herbivory accidental.

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS

Changes in biodiversity and other environmental changes ous environment: gametes released into the water column are influence each other, in marine systems as well as in terres- quickly dispersed, and most species are highly fecund and time trial. Biodiversity loss can reduce an ecosystem’s resilience to their spawning to release gametes en masse (Kenchington and environmental perturbation. This can be brought about by, Agardy, 1990). Perhaps most importantly, physical features of for example, climate change (warming), ozone depletion (in- the marine ecosystem dictate its character, more so than on creased radiation), and pollution (eutrophication, toxics). All of land (Agardy, 1999). these impacts can also reduce biodiversity. Diverse marine systems in which neither species, population, nor genetic di- In the marine environment, all habitats are ultimately con- versity has been severely constricted, are better able to adapt nected – and water is the great connector. Some habitats to changing environmental conditions (Norse, 1993). Un- are more intimately and crucially linked, however. Coral reefs altered coral reefs, for instance, are less likely to experience provide a good example of this interconnectedness. For years, disease-related mortality when ocean temperatures increase diverse and biologically rich coral reefs were thought of as (Birkeland, 2004). However, all environmental change has the self-contained entities: very productive ecosystems with nu- potential to cause biodiversity loss, especially at the level of trients essentially locked up in the complex biological com- genes and populations. The greater the magnitude and the munity of the reef itself. However, many of the most crucial more rapid the rate of change, the more likely biodiversity nursery habitats for reef organisms are actually not on the will be affected, and the greater the probability that subse- coral reef itself, but rather in seagrass beds, mangrove forests, and quent environmental change will lead to greater ecosystem sea mounts sometimes far removed from the reef (Hatcher degradation (MA, 2005a). et al., 1989). Currents and the mobile organisms themselves provide the linkages among the reefs, nursery habitats, and Comparisons Between Marine and Terrestrial places where organisms move to feed or breed (Mann and Systems Lazier, 1991; Dayton et al., 1995). Thus, managing marine systems like coral reefs requires addressing threats to these es- Marine and terrestrial systems exhibit differences in scale sential linked habitats as well. and process (Steele, 1985). The obvious distinction is that on land, air is the primary medium for food transmission, and The ocean and coastal habitats are not only connected to each in marine systems, water is the primary medium. Although other, they are also inextricably linked to land (Agardy, 1999). both terrestrial and marine systems exist in three-dimen- Although the terrestrial systems are also linked to the sea, this sional space, land-based ecosystems are predominantly two- converse relationship is neither as strong nor as influential as dimensional, with most ecological communities “rooted” to is the sea to land link. Freshwater is the great mediator here. the earth’s surface. The seas present a different picture, with Rivers and streams bring nutrients as well as pollutants to the bulk of life moving about in a non-homogeneous space, the ocean, and the ocean gives some of these materials back and few processes linking the water column with the benthos. to land via the atmosphere, tides, and seiches. Other pathways The water medium has freed organisms from the constraints include the deposition of anadromous fish (Deegan, 1993). on body type posed by gravity, thus the array of life, as ex- Many coastal habitats, such as estuaries, are tied closely to pressed by phyletic diversity, is much wider in the sea (Kench- land, and are greatly affected by land use and terrestrial habitat ington and Agardy, 1990; Norse, 1993). In the sea and its alteration (MA, 2005b). coastal interface, the transport of nutrients occurs over vast distances, and both passive movement and active migrations In coastal and marine systems, habitats include freshwater and contribute to its highly dynamic nature. Marine species must brackish water wetlands, mangrove forests, estuaries, marshes, also meet the challenges posed to reproduction in an aque- lagoons and salt ponds, rocky or muddy intertidal areas, beaches

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS 10

and dunes, coral reef systems, seagrass meadows, kelp forests, cartilaginous fishes, reptiles (sea turtles, sea snakes, marine nearshore islands, semi-enclosed seas, and nearshore coastal iguanas), mammals (sea otters, manatees and dugongs, seals, waters of the continental shelves. Many of these coastal sys- whales and dolphins) and birds (seabirds, shorebirds, etc.). tems are highly productive and rival the productivity of even the most productive terrestrial systems (MA, 2005b). Table 1 Species richness is valued as the common currency of the illustrates the relative productivity of some of these coastal diversity of life - the “face” of biodiversity. The problem with ecosystems in comparison to select terrestrial ecosystems. this emphasis is the potential masking of important trends and properties, beyond taxonomy (MA, 2005a). Table 1: Relative productivity estimates for select coastal and Given the complexity of biodiversity, species- terrestrial ecosystems or other taxon-based measures-rarely reflect Ecosystem type Mean net primary productivity Mean biomass per unit the real attributes that provide insight into -2 -1 2 (g.m. year ) area (kg/m ) roles and functions. There are several limita- Swamp and march 2000 15 tions associated with the emphasis on species. Continental shelf 360 0.01 First, what constitutes a species is often not well defined (MA, 2005a). For example, it Coral reefs and kelp 2500 2 is not necessarily easy to know when one is Estuaries 1500 1 measuring population or species diversity. In- Tropical rain forest 2200 45 deed, the dynamic nature of marine systems Source: Modified from Table 3-4 in Odum and Barnett, 2004 confounds the species/population dichotomy, since members of the same marine species are Marine Organisms and Environments often isolated by populations so discrete that intermixing is functionally impossible (see discussion of genetic diversity, Marine Biodiversity below).

Habitat diversity Second, species richness and ecosystem function may not Biodiversity is defined as the variety of life in all of its forms. correlate well. Productive ecosystems, such as estuaries or Although we usually think of diversity in terms of species wetlands, are often species poor. Third, although species are numbers, an equally important metric is the amount of vari- taxonomically equivalent, they are rarely ecologically equiva- ability of habitat within a unit area, or the spatial autocorrela- lent. For example, taxa that are ecosystem engineers, like bea- tion of species within an area (MA, 2005a). This is broadly vers or marine worms, and keystone species, whose presence known as beta-diversity (see the What is Biodiversity module). maintains a diverse array of species in a community, often The oceans and coastal areas exhibit a vast array of habitat make greater contributions to ecosystem functions than oth- types, and many ecosystems are highly diverse at this level of ers. Fourth, species vary extraordinarily in abundance, often organization. exhibiting a pattern in which only a few are dominant, while many are rare (MA, 2005a). Thus, to simply count taxa does Phyletic and species diversity not take into consideration how variable each might be in its Phyletic diversity in the sea is much greater than on land. contribution to ecosystem properties. Major marine phyla include microbes, such as protists, fungi, bacteria, archaea; plants such as algae and flowering plants like Genetic diversity sea grasses; invertebrates such as sponges, cnidarians, echinoderms, The fundamental differences in marine and terrestrial ecosys- mollusks, crustaceans; and vertebrates, including the bony and tems are in degree, not in kind (Steele, 1995). But there are

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS 11

semantic problems that arise from the different ways we label tive mixing is a zone of rapid transition, where (in most situ- marine systems and those on land. Understanding species di- ations) temperature decreases rapidly with depth. This transi- versity and genetic diversity in the sea is a case in point. Most tion layer, called the seasonal thermocline, is shallow in spring marine species are widespread in distribution, being cos- and summer, deep in autumn, and disappears in winter. In the mopolitan or even circumglobal. However, marine popula- tropics, winter cooling is not strong enough to destroy the tions are structured into distinct demes, such that the genetic seasonal thermocline, and a shallow feature, sometimes called make-up of a population or stock can be profoundly different the tropical thermocline, is maintained throughout the year from that of a neighboring stock or population, even though (Tomczak, 2000). we refer to them as being of the same species. The depth range from below the seasonal thermocline to Physical Oceanography about 1000 m is known as the permanent or oceanic thermocline. It is the transition zone from the warm waters of the Physical Environment at Various Scales surface layer to the cold waters of great oceanic depth. The temperature at the upper limit of the permanent thermocline The physical environment of the oceans drives their biological depends on latitude, reaching from well above 20°C in the make-up to a greater degree than in terrestrial systems. The tropics to just above 15°C in temperate regions. At the lower oceanographic phenomena that underlie how the oceans are limit, temperatures are rather uniform around 4 - 6°C, de- structured and how they function occur at three scales. The pending on the particular ocean (Tomczak, 2000). first is the macro-scale, on which large-scale hydrographic processes and patterns manifest themselves in oceanographic Meso scale oceanography circulation and major currents. On the meso-scale, temperature Ocean and atmosphere form a coupled system. The coupling and salinity create thermohaline regimes. On the micro-scale, occurs through exchange processes at the sea surface intertidal exchange, upwelling, and longshore currents frame the face (Tomczak, 2000). These determine the energy and mass physical environment of different marine habitats in different budgets of the ocean. In the North Atlantic, for example, solar coastal and continental shelf areas. heating and excess evaporation over precipitation and runoff creates an upper layer of relatively warm, saline water in the Macro scale oceanography tropics. Some of this water flows north, through the passages Although the ocean waters appear homogeneous, there are between Iceland and Britain. On the way it gives up heat to both stratification into horizontal layers and vertical mixing the atmosphere, particularly in winter. Since winds at these between layers that take place below the visible surface. The latitudes are generally from the west, the heat is carried over surface layer, with uniform hydrographic properties, is an es- Europe, producing the mild winters that are so character- sential element of heat and freshwater transfer between the istic of that region, relative to others at similar latitudes. So atmosphere and the ocean. It usually occupies the uppermost much heat is withdrawn that the surface temperature drops 50 - 150 m, but can reach much deeper. Winter cooling at the close to the freezing point. This water, now in the Green- sea surface produces convective overturning of water, releas- land Sea, remains relatively saline, and the combination of ing heat stored in the ocean to the atmosphere. During spring low temperature and high salinity makes the water denser and summer, the mixed layer absorbs heat, moderating the than deeper water below it. Convection sets in and the water earth’s seasonal temperature extremes by storing heat until sinks - occasionally and locally right to the bottom. There the following autumn and winter. Mixing is achieved by the it slides under and mixes with other water already close to action of wind waves, which cannot reach much deeper than the bottom, spreading out and flowing southward, deep. This a few tens of meters, and tidal action. Below the layer of ac- thermohaline circulation (warm surface water flowing north,

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS 12

cooling, sinking and then flowing south) provides an enor- most obvious expression of tides is the rise and fall in sea level. mous northward heat flux (Stewart, 1991). Equally important is a regular change in current speed and direction; tidal currents are among the strongest in the ocean. Circulation at the surface of the oceans is wind-driven. It is If the tidal forcing is in resonance with a seiche period for the generally referred to as zonal or meridian flow, depending sea or bay, the tidal range is amplified and can be enormous, on whether it is predominantly across latitudes or longitudes such as occurs in the Bay of Fundy on the Canadian east (IPCC, 2003). Under about 1 kilometer of depth, however, coast, which with 14 meter tides has the largest tidal range in water flows are not driven by wind but rather by tempera- the world (Tomczak, 2000). ture (thermal) and salinity (haline) effects. This is known col- lectively as thermohaline circulation. The driving force for Longshore currents result from coastal topography, and are thermohaline circulation is water mass formation. Water highly influenced by coastal constructions such as breakwa- masses with well-defined temperature and salinity are created ters, jetties, seawalls, etc. Perhaps even more than tidal regimes, by surface processes in specific locations. They then sink and longshore currents influence the distribution and abundance mix slowly with other water masses as they move along. The of coastal marine organisms. Even offshore marine biodiver- two main processes of water mass formation are deep convec- sity is affected by longshore currents, since some pelagic spe- tion and subduction, which are linked to the dynamics of the cies have some life stages in nearshore waters (MA, 2005b). mixed layer at the surface of the ocean (Tomczak, 2000). Upwellings are vertical currents that deliver cold, nutrient- rich bottom waters to the surface (Tomczak, 2000). The most The thermohaline circulation described above has become productive areas of the ocean are upwellings, including the known as the ‘Great Ocean Conveyor Belt’ (Tomczak, 2000). Benguela upwelling off southwest Africa, and the Humboldt The water that sinks in the North Atlantic Ocean (North upwelling off Peru. These major upwellings are the product Atlantic Deep Water) enters the Antarctic Circumpolar Cur- of the movement of cold bottom water hitting the edge of rent and from there, all ocean basins, where it rises slowly the continents and flowing upwards as a result; however, there into the upper kilometer and returns to the North Atlantic in are many minor upwellings that occur in places where the the permanent thermocline. Although this is only one of the bottom topography influences deepwater currents. Upwell- circulation paths of North Atlantic Deep Water, it is the most ing areas may not be particularly diverse in species per unit important from the point of ocean/atmosphere coupling, area, but they support geographically massive food webs that since it acts as a major sink for atmospheric greenhouse gases. include many marine organisms and seabirds. The extent to The only other region of similar importance is the Southern which upwellings provide a foundation for extensive food Ocean, where Antarctic Bottom Water sinks. webs is highlighted by what happens during El Nino South- ern Oscillation events in which upwelling flows diminish and Micro scale oceanography large numbers of organisms, especially seabirds, starve. Tides, longshore currents, and upwellings also affect the ecology of marine areas. Tides are long waves caused by the force Links Between Physical Oceanography and Biota of gravity from the moon. The dominant period of tidal cycles usually is 12 hours 25 minutes, which is half a lunar day There is a strong correspondence between physical features (Tomczak, 2000). Tides are generated by the gravitational po- in the ocean environment and biodiversity, irregardless of tential of the moon and the sun, and their propagation and whether those features have to do with bottom topography or amplitude are influenced by friction, the rotation of the earth, ocean circulation. In general, the more complex and hetero- known as Coriolis force, and resonances determined by the geneous the physical environment, the more productive and shapes and depths of the ocean basins and marginal seas. The diverse are the food webs supported by it. Marine food webs

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS 13

are based largely on primary production by microscopic algae, by smaller, shorter-lived fishes at lower trophic levels. Globally, the phytoplankton. This occurs in the lighted, upper layers of both the landings and their mean trophic levels are currently the ocean, especially the coastal zone. Production is intensified going down under the pressure of fisheries (MA, 2005c). by processes that lift nutrient-laden water from deeper layers. Most of this production is then either grazed by herbivo- Major Marine Ecosystems rous zooplankton (mainly copepods), or falls to the sea bottom in the form of detritus aggregates known as marine snow. It Nearshore Ecosystems is attacked by bacteria on the way down, and consumed by benthic organisms upon reaching the sea bottom. Little ma- Kelp forests and hard bottoms rine snow reaches the bottom of tropical seas due to, among Kelp forests are distinctive for the structure provided by the other things, the higher metabolic rates of bacteria in warm very large, anchored macroalgae that give this temperate habi- waters. Hence, there is less benthos, and fewer ground fish to tat type its name; they occur in many different canopy types. catch in the deeper reaches of tropical seas, than in otherwise The productivity of kelp ecosystems rivals that of the most comparable temperate or polar seas. This creates a limit for productive land systems, and they are remarkably resilient to the expansion of deep-sea bottom fisheries in tropical areas natural disturbances. They are highly diverse systems orga- (MA, 2005c). nized around large brown algae, and the complex biological structure supports a high variety of species and interactions The higher the trophic level, the lower the biological produc- (Dayton, 2003). They support fisheries of various inverte- tion. In other words, the farther organisms are from phyto- brates and finfish, and the kelps themselves are harvested. Kelp plankton and other primary producers, the smaller the pop- communities have many herbivores, but the most important ulation size and biomass. In fishes, the greatest production are sea urchins, capable of consuming nearly all fleshy algae in occurs at a trophic level of 3 (small fishes such as sardines most kelp systems. Unfortunately, predators which help keep and herrings that feed on herbivorous zooplankton), and near urchins in check within kelp forests have been destabilized trophic level 4 (fish such as cods and tunas that prey on zoo- by fishing to such an extent that the kelp forests retain only a planktivorous fishes). Many fish, however, have intermediate fraction of their former diversity (Dayton et al., 1998; Tegner trophic levels, as they tend to feed on a wide range of food and Dayton, 2000). items, often feeding on zooplankton as juveniles and feeding on other fish as adults (Pauly et al., 1998). Biomass energy is The temperate kelp forest is one of the best-understood ma- transferred up the food web with transfer efficiencies between rine communities in the world in terms of local processes at trophic levels ranging in marine ecosystems from about 5% work at a particular time and location (Dayton, 2003). It is a to 20%, with 10% a widely accepted mean (MA, 2005c). This system dominated by patch dynamics based on frequent dis- implies that the productivity of large, higher trophic level fish turbance, effective dispersal, and both inhibitory and faculta- that have traditionally been targeted in the most lucrative tive succession. Strong and weak interactions are well studied fisheries is lower than that of less desirable, lower trophic level at the small scales (Paine, 2002). However, discerning the dif- fishes. However, historical fishing has followed a path now ferences between direct human impacts from natural changes known as “fishing down the food web” (Pauly et al., 1998), or changes related to regional or global change has proven in which the natural proportion of predators and producers difficult. has been grossly altered, skewed towards the lowest trophic levels. This process is occurring as a result of the susceptibility The paradigm of fishing impacts on coastal habitats cascad- to fishing pressure of large, slow-growing high trophic level ing down to much simplified sea urchin-dominated barren fishes, which are gradually being replaced, in global landings, grounds has proven very general (Sala et al., 1998; Steneck,

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS 14

1998). The actual mechanisms, however, vary across systems. While robust to natural disturbances from predation, compe- No kelp forest is pristine, and humans have vastly reduced tition, and biofouling, the fact that the species in these sys- expectations of how the systems should exist. For example, tems tend to have extremely limited larval dispersal means in the Atlantic large fish such as halibut, wolfish, and cod are the recolonization and recovery following perturbation can the key predators of sea urchins. These predators largely have be very slow (Dayton, 2003). Lissner et al. (1991) consider been removed from the system, and, as a result, sea urchin many types of disturbances and the subsequent succession and populations have exploded (Witman and Sebens, 1992; Ste- recovery to the original association. Large disturbances, such neck, 1998). Then, directed exploitation and disease have led as widespread damage from fishing gear, almost never allow to a collapse of the urchin populations leaving a once healthy recovery to the pre-existing condition (Dayton, 2003). and productive ecosystem degraded by waves of exotic species (Harris and Tyrell, 2001). Estuaries and tidal wetlands such as mangroves Estuaries—areas where the freshwater of rivers meets the salt- Non-kelp forested hard bottom communities are also highly water of the oceans—are highly productive, dynamic, ecolog- productive, and important for fisheries. Below thephotic zone ically critical to other marine systems, and valuable to people. these tend to be dominated by sponges, corals, bryozoans, and Worldwide, some 1200 major estuaries have been identified compound ascidia (Dayton, 2003). The architectural com- and mapped, yielding a total digitized area of approximately plexity provided by these colonies of organisms is important 500,000 square kilometers (MA, 2005b). Estuaries and associ- to supporting other living beings. They provide refuge from ated marshes and lagoons play a key role in maintaining hy- predators, and generally play an important role in maintaining drological balance, filtering water of pollutants, and providing the biodiversity and biocomplexity of the seafloor (Levin et habitat for birds, fish, mollusks, crustaceans, and other kinds al., 2001). In the more stable habitats, the species present are of ecologically and commercially important organisms (Beck usually clones and long-lived individuals, and the associations et al., 2001; Levin et al., 2001). The 1200 largest estuaries, in- are stable over decades and perhaps centuries. The popula- cluding lagoons and fiords, account for approximately 80% of tions are marked by very low dispersal, often with larvae that the world’s freshwater discharge (Alder, 2003; Figure 1 shows crawl only centimeters during their larval lifespan, and they the largest of the world’s estuaries). Of all coastal subtypes, are characterized by extreme resistance to competition, inva- estuaries and marshes support the widest range of services, sion, or predation (reviewed in Dayton, 1994). and may be the most important areas for ecosystems services. One of the key processes is the mixing of nutrients from up- Encrusting communities often appear to have several exam- stream as well as from tidal sources, making estuaries one of ples of alternative stable states that are self-perpetuating in the the most fertile coastal environments (Simenstad et al., 2000). face of normal disturbances (Sebens, 1986). The mechanisms There are many more estuarine-dependent than resident spe- involve powerful, often chemical, defenses from predation and cies, and estuaries provide a range of habitats to sustain diverse biofouling, asexual reproduction or non-dispersing larvae, and flora and fauna (Dayton, 2003). Estuaries are particularly im- the ability to protect juveniles from predation (Dayton, 2003). portant as nursery areas for fisheries and other species, and Witman and Sebens (1992) demonstrated that overfishing form one of the strongest linkages between coastal, marine, along the coastal zone greatly reduced the top predators and and freshwater systems and the ecosystem services they pro- caused population explosions in their prey. This in turn has vide (Beck et al., 2001). changed much of the community structure. Aronson (1991) argues that this overfishing has virtually eliminated many Estuaries and coastal wetlands are critical transition zones evolutionarily “new” predators and released a “rebirth” of the linking the land and sea (see review by Levin et al., 2001). Mesozoic communities dominated by echinoderms. Important nutrient cycling and fluxes, primary and second-

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS 15

ary productivity, nursery areas, and critical habitats of many and global mangrove forest cover currently is estimated be- birds and mammals are examples of essential services provided tween 16 and 18 million hectares (Spalding et al., 1997; Valiela by this once ubiquitous habitat. Most of these functions are et al., 2001). The majority of mangroves are found in Asia. mediated via sediment-associated biota including macrophytes Mangroves grow under a wide amplitude of salinities, from (mangroves, salt marsh plants, and sea grass beds as well as almost freshwater to 2.5 times seawater strength. They may be macro algae), heterotrophic bacteria and fungi, and many in- classified into three major zones (Ewel et al., 1998) based on vertebrate taxa. Functional groups (organisms with similar dominant physical processes and geomorphological charac- roles) include roles such as decomposition and nutrient recy- ters: a) tide-dominated fringing mangroves, b) river-dominat- cling, resuspension, filter feeding, and bioturbation. ed riverine mangroves, and c) interior basin mangroves. The importance and quality of the goods and services provided by Plants regulate many aspects of the nutrient, particle, and mangroves varies among these zones in terms of habitat for organism dynamics both below and above ground. Further, animals, organic matter export function, reducing soil erosion, they often provide critical habitats for endangered vertebrates. protection from typhoons, etc. (Ewel et al., 1998). Importantly, a wide variety of animals move in and out of this habitat for many reasons, including the completion of Soft sediments and sea mounts life cycles, feeding, use of larval nurseries, and migration. The About 70% of the earth’s seafloor is composed of soft sedi- bioturbation (or movement of sediment by burrowers) is itself ment (Dayton, 2003). Although soft-sediment habitats do not

Figure 1: Distribution of major estuaries around the world

Modified from: MA, 2005b an important structuring mechanism, providing mounds and always appear as highly structured as some terrestrial or ma- depressions that serve as habitats to hundreds of small inverte- rine reef habitats, they are characterized by extremely high brate species (Dayton, 2003). species diversity. There is now strong evidence of fishing effects on seafloor communities that have important ramifi- Mangroves are trees and shrubs found in intertidal zones and cations for ecosystem function and resilience (Rogers et al., estuarine margins that have adapted to living in saline water, 1998; Steneck, 1998; Dayton, 2003). Given the magnitude either continually or during high tides (Duke, 1992). Man- of disturbance by trawling and dredging and the extension of grove forests are found in both tropical and subtropical areas, fishing effort into more vulnerable benthic communities,

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS 16

this type of human disturbance is one of the most significant major coral reef ecosystems is shown in Figure 2. Reef for- threats to marine biodiversity (Dayton, 2003). Sponge gardens mations occur as barrier reefs, atolls, fringing reefs, or patch in soft substrates face particular threat from bottom trawling, reefs, and many islands in the Pacific Ocean, Indian Ocean since the soft substrate is easily raked by heavy trawling gear and Caribbean Sea have extensive reef systems occurring in (MA, 2005). a combination of these types. Coral reefs occur mainly in relatively nutrient-poor waters of the tropics, yet because nu- Apart from their extremely high species diversity, soft-sedi- trient cycling is very efficient on reefs, and complex preda- ment marine organisms have crucial functional roles in many tor-prey interactions maintain diversity, productivity is high. biogeochemical processes that sustain the biosphere (Dayton, However, with a high number of trophic levels, the amount 2003). Within the sediments, microbial communities drive of primary productivity converted to higher levels is relatively nutrient recycling. In addition, the movement, burrowing, low, and reef organisms are prone to overexploitation. and feeding of organisms such as worms, crabs, shrimps, and sea cucumbers, markedly increase the surface area of sedi- The fine-tuned, complex nature of reefs makes them high- ment exposed to the water column. This affects nutrient rely vulnerable to negative impacts from over-use and habitat cycling back into the water column, where it can again fuel degradation. When particular elements of this interconnected primary production. Organic debris produced on the conti- ecosystem are removed, negative feedbacks and cascading ef- nental shelf finds its way to the shelf edge, where it accumu- fects occur (Nystrom et al., 2000). Birkeland (2004) describes lates in canyons that act as sinks to the deep ocean. There, it ecological ratcheting effects through which coral reefs are supports extremely high densities of small crustaceans that in transformed from productive, diverse biological communities turn serve as prey for both juvenile and mature fish (Vetter into depauperate ones, and similar cascading effects caused and Dayton, 1998). by technological, economic, and cultural phenomena. Coral reefs are one of the few marine ecosystems displaying distur- The ocean floor’s soft sediment is interrupted by highly bance-induced phase shifts. This phenomenon causes diverse structured seamounts with highly diverse communities of reef ecosystems dominated by stony corals to dramatically organisms (Dayton, 1994). These underwater mountains or turn into biologically impoverished wastelands overgrown volcanoes are usually found far offshore and are thought to be with algae (Bellwood et al., 2004). Reefs are highly vulner- crucial for many pelagic fish species. They are sites for breed- able to being negatively affected by global warming; rising ing and spawning, as well as safe havens for juvenile fishes sea temperatures cause coral bleaching, and often subsequent seeking refuge from open ocean predators (Johannes et al., mortality. 1999). Because their high species diversity is concentrated into a relatively small, localized area, and because of their oc- Seagrass beds casionally high endemism, sea mounts are extremely vulner- Seagrass is a generic term for the flowering plants that usually able to fishing impacts. colonize soft-bottomed areas of the oceans from the tropics to the temperate zones (some seagrass can be found on hard- Coral reefs bottomed areas but the areas occupied are usually small). In Coral reefs exhibit high species diversity and endemism and estuarine and other nearshore areas of the higher latitudes, are valued for their provisioning, regulating, and cultural ser- eelgrass (e.g. Zostera spp.) forms dense meadows (Deegan and vices (McKinney, 1998). Reef-building corals occur in tropi- Buchsbaum, 2001). Further towards the tropics, manatee and cal coastal areas with suitable light conditions and high salin- turtle grass (e.g. Thalassia testudinum and Syringodium filiforme) ity, and are particularly abundant where sediment loading and cover wide areas. These popular names are due to the im- freshwater input is minimal. The distribution of the world’s portant role seagrass plays as the main food source of these

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS 17

Figure 2: Global distribution of major coral reefs

(a) East Indian and Western Pacific Oceans (b) Middle East

(e) Caribbean (f) Oceania

Modified from: UNEP-World Conservation Monitoring Centre, 2003

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS 18

large, herbivorous vertebrates. Along with mangroves, seagrass of communities of marine organisms. In the Mediterranean is thought to be particularly important in providing nursery Sea, for instance, a frontal zone and associated upwelling area areas in the tropics, where it provides crucial habitat for coral in the Ligurian Sea is distinctive because of the large diversity reef fishes and invertebrates (Gray et al., 1996; Heck et al., of marine mammals and other marine animals that congre- 1997). This is a highly productive ecosystem, and an impor- gate there to feed (see NCEP case study on The Pelagos Sanc- tant source of food for many species of coastal and marine tuary for Mediterranean Marine Mammals). organisms in both tropical and temperate regions (Gray et al., 1996). Seagrass also plays a notable role in trapping sediments The water column habitats of the world ocean can be sub- and stabilizing shorelines. divided into biomes. Although marine biogeographers have long struggled to classify the oceans according to not only Seagrass continues to play an important ecological role even the physical environment but also the biotic one, much as once the blades of grass are cut by grazers or currents and are the Udvardy classification of terrestrial ecosystems, today the carried by the water column. Drift beds, composed of mats of most widely accepted system is that of Longhurst (1998) who seagrass floating at or near the surface, provide important food divides the world ocean into four major biomes (see Figure and shelter for young fishes (Kulczycki et al., 1981). In addi- 3). tion, the deposit of seagrass castings and macroalgae remnants on beaches is thought to be a key pathway for nutrient pro- The Coastal Boundary Zone biome (10.5% of the world visioning to many coastal invertebrates, shorebirds, and other ocean) consists of the continental shelves (0-200 m) and the organisms. For instance, nearly 20% of the annual production adjacent slopes, i.e., from the coastlines to the oceanographic of nearby seagrass (over 6 million kg dry weight of beach front usually found along the shelf-edges (Longhurst, 1998). cast) is deposited each year on the 9.5 km beach of Mombasa From a conservation point of view, this is the most important Marine Park in Kenya, supporting a wide variety of infauna portion of the world ocean, since this is where human uses of, and shorebirds (Ochieng and Erftemeijer, 2003). and impacts on, marine resources is the greatest.

Tropical seagrass beds or meadows occur both in association The Trade-winds biome (covering 38.5% of the world’s with coral reefs and removed from them, particularly in shal- oceans) lies between the boreal and austral Subtropical con- low, protected coastal areas such as Florida Bay in the United vergences, where a strong density gradient hinders nutrient States, Shark Bay and the Gulf of Carpentaria in Australia, and regeneration. The resulting low levels of new primary pro- other geomorphologically similar locations. Seagrass is also duction make these zones the marine equivalent of deserts pervasive (and ecologically important) in temperate coastal (MA, 2005c). Therefore, fisheries in this biome rely mainly areas such as the Baltic Sea (Fonseca et al., 1992; Isaakson et on large pelagic fishes, especially tunas, capable of migrating al., 1994; Green and Short, 2003). over the long distances that separate isolated food patches. In the eastern tropical Pacific, a major portion of the tuna purse- Offshore Open Water seine catch results from exploitation of a close association with pelagic dolphins, which suffered severe depletion due The largest marine habitat by area or volume is offshore open to incidental kills in the tuna seines (Gerrodette, 2002). One water. This accounts for close to 55% of the earth’s surface, exception to the general low productivity of the Trade-winds providing nearly 90% of the living space of the biosphere. biome is around islands and seamounts, where physical pro- This offshore open water is not homogenous, however. cesses such as localized upwelling allow for localized enrich- Ocean circulation creates both pelagic water masses and dy- ment of the surface layer. Above seamounts, these processes namic frontal zones, both of which influence the distribution also lead to the retention of local production and the trapping

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS 19

of advected plankton, thus turning seamounts into oases char- mary producers from both open waters and under the ice and acterized by endemism and, when pristine, high fish biomass. then serves as food for a vast number of predators, notably finfishes, birds (especially penguins), and marine mammals In the Westerlies biome (35.7% of the world’s oceans), sea- (MA, 2005c). sonal differences in mixed-layer depth are forced by seasonality in surface irradiance and wind stress, inducing strong Marine Ecology seasonality of biological processes, characteristically including a spring bloom of phytoplankton (MA, 2005c). The fisheries Marine Population Ecology of this biome, mainly targeting tuna and other large pelagics, are similar to those of the Trade winds biome. Life history Conservation and restoration decisions rest on understand- The Polar biome covers 15% of the world ocean and accounts ing the processes that result in population changes, ecosystem for 15% of global fish landings. The noteworthy productivity stability, and succession. There are important thresholds in of this biome results from vertical density structure deter- populations and ecosystems, relating to critical stages in the mined by low-salinity waters from spring melting of ice. The life histories of the populations, as well as to the roles popula- bulk of annual primary production occurs in ice-free waters tions play with regard to the resiliency of the ecosystems to as a short intense summer burst. Primary production under natural and anthropogenic stress. lighted ice occurs over longer periods, especially in Antarc- tica. The Antarctic krill, Euphausia superba, consumes the pri- For marine systems such questions have focused on recruit-

Figure 3: Longhurst classification of ocean biomes The coastal boundary is indicated by a black border around each continent. Each of these biomes is subdivided into Biogeographical Provinces (BGP). The BGP of the coastal boundary biome largely overlaps with the LEMs identified by K. Sherman.

Taken from: MA, 2005c, adapted from Longhurst, 1998

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS 20

ment dynamics, and while there are also many higher order for conservation and management (Dayton, 2003). As on processes such as productivity and turnover rates, understand- land, marine species exhibit a wide variety of fertility pat- ing recruitment constitutes a logical beginning towards com- terns, which can be categorized as either R- or K- selected. prehending population and ecosystem thresholds (Dayton, R-selected species have high fertility and are usually free- 2003). Variously defined, ecologists have attempted to iden- spawning, with little to no parental care. K-selected species tify sources, sinks, and essential habitats as important factors of have significantly lower fertility (and usually longer life spans), recruitment processes. Despite definitions, questions remain: but exhibit brooding and more parental care. how does one operationally define sources and sinks or rank habitat qualities? How can habitats be placed along a source- Larval ecology and recruitment sink gradient? Critical periods and thresholds or bottlenecks Critical periods in the planktonic life of fish and other ma- can vary in time and space: how do we rank and study them rine larvae include time of first feeding, successful dispersal to with regard to declining populations and fragile ecosystems appropriate habitats, settlement, and metamorphosis (Hjort, without understanding the relevant natural history? In most 1914). The first feeding periods are defined by the abilities of marine systems the following life-history components are im- the larvae to handle prey, as well as sufficient density of appro- portant and have distinct thresholds (Dayton, 2003). priate prey. Invertebrates have much more complicated life history patterns and dispersal tactics, with post-fertilization Reproduction and dispersal processes varying from seconds for brooding Fertilization of gametes is essential, and tactics for achieving species, to many months for organisms with feeding larvae. this are well known for the birds and bees of the terrestrial world. Fertilization tactics are often very different in the sea, Most propagules depend on oceanographic transport. The lar- however, where dilution of gametes for broadcast spawners vae of most species with planktonic dispersal drift for periods implies that individuals must release sperm and eggs within a of 3 to 60 days. Because of complicated coastal oceanography, meter or so of each other (Tegner et al., 1996). Fertilization the differences within this period of time often encompass of relatively sedentary species such as abalone, scallops, sea complex and very different physical transport systems. This urchins, and bivalves often depends on the existence of dense is especially true in the very near shore areas. These include patches of males and females, or en masse spawning. The those within/between bays, kelp forests, or unstable gyres Allee effect describes the relationship between high numbers where “relaxation” modes are important, and the oceanog- of reproducing adults and successful subsequent recruitment raphy is complicated. The variability in these factors com- of young – in some systems, management must take these plicates the definition of sources and sinks for species such as Allee effects into account. In many cases, the feature that at- lobsters, and some echinoderms with very long larval periods tracts spawning aggregations is a biologically produced physi- (Dayton, 2003). cal structure, such as a coral reef. For example, Koenig et al. (1996) report that Florida groupers traveled over 100 miles Dispersal processes are highly variable in evolutionary adapta- to gather around deep-water Oculina coral reefs to spawn. tions and the physical transport systems they utilize. Marine Similar roles are likely to be played by other deep-water coral ecologists often focus on dispersal biology, but many systems, reefs, most of which have been virtually obliterated in the such as the clonal encrusting ones, have virtually no dispersal Aleutian Islands, Nova Scotia, Scotland, Norway, and espe- (Dayton, 2003). Most reproduce by budding or crawl-away cially the Southern Ocean seamounts. larvae (Levin et al., 2001). In the same sense, many other soft- bottom groups including peraicarid crustacea and capitellid How particular species are adapted to ecological conditions, polychaetes are brooders and disperse as adults; their transport including predation pressure and competition, is important systems include the bottom flocculent layer or being picked up

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS 21

and carried by complicated breaking internal waves. planktonic drifting. Recent research suggests that sound may have a role to play in coral settlement (Simson et al., 2005). Successful settlement is another critical period (Tegner and Environmental inducements are sometimes needed for larvae Dayton, 1977). Food availability and temperature strongly in- to settle and metamorphose. According to Dayton, species fluence the length of time spent in the water column. The pe- with the longest precompetent periods also have very specific riod at which a larva becomes capable of settlement is known recruitment habitats that help avoid predation, disturbance, as the competent phase. The larva may continue to drift, ex- and stress (Dayton et al., 1995). posing itself to increased risk of predation before it settles. Models of Jackson and Strathmann (1981) demonstrate that Juveniles and adults often have different habitats. For exam- critical parameters are mortality rates, the length of the pre- ple, nurseries of many Pacific rockfish are in kelp forests, and competent period, and the ratio of competent/precompetent many other species rely on sea grass beds, mangroves, corals, time. These factors are poorly understood but extremely im- various associations of encrusting species, or depressions in portant and probably account for the common observation of soft bottom habitats. In many cases the adults live in very episodic settlement. different habitats and migration may be tenuous and risky. Without understanding this natural history, artificial settle- Availability of appropriate settlement habitats or nurseries ment areas such as man-made reefs may simply be killing can be an important bottleneck, and much is left to chance zones if the appropriate adult habitats are not available. (Sale, 1991). Many unanswered questions remain about how young locate appropriate settlement areas, especially those Community Ecology species that show natal homing. For instance, much as sea turtles return to the nesting beach where they were hatched Communities of organisms, whether in the sea or on land, in order to lay eggs, coral larvae also must find the reef after respond in predictable ways to the forces of interspecific and intraspecific predation and competition. The intertidal communities of temperate regions provided many of the experiments that led to this understanding: most famous of all were the studies by Paine and colleagues, who removed the top predator Pisaster (a species of sea star) from intertidal rock pools and observed the decline in species diversity that resulted (see Paine, 2002, for a review of earlier studies and new results). Removal of predators can have this effect because top predators keep their prey populations down in number so that none can dominate. When this sort of predation pressure stops, species that were formerly controlled by predator populations are “released” and multiply, upsetting the original biodiversity balance. When such perturbations cause effects across the entire food web, they are known as “cascading effects,” because impacting the top trophic level subsequently impacts the trophic levels below it.

Indian lionfish Pterios( muricata) off of the Seychelles Kelp forest communities are well studied in regards to cascad- (Source: K. Frey) ing effects. At the bottom of the kelp community food web

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS 22

are seaweeds (kelps and other algae) and microscopic plank- Bahamas, Mumby (2006) studied the effects of removing par- tonic algae, both of which serve as the primary producers in rotfish on the health and diversity of reefs across a wide area. this ecosystem. The planktonic algae support small planktonic Removing even small numbers of these grazers can have dra- invertebrates such as copepods, which in turn are consumed matic effects on reef communities, influencing the amount of by filter-feeding sessile invertebrates such as hydroids, scal- coral cover, biomass of reef species, and reef species diversity. lops, barnacles, sea anemones, bryozoans, and tube worms, as The reason for this is that herbivores like parrotfish keep algae well as other smaller mobile predators like fish and certain from overgrowing the reef and diminishing the availability of crustaceans. The larger seaweeds are eaten both directly by niches for other reef species (including corals, sponges, crus- a broad range of animals, including sea urchins, fishes, small taceans, mollusks, and fishes). snails, shrimp-like crustaceans, sea stars, and crabs, and indirectly (as large and small loose pieces of “drift”) by abalones, These community effects seem most pronounced in ecosys- sea urchins, mussels, and barnacles. Many of these animals are tems that are relatively closed systems, and where food is a key then consumed by mid-level predators, such as other sea stars, limiting factor. In more open systems in which food is readily larger crabs, larger fishes, and octopuses. available, such as major upwelling systems like the Benguela or Peruvian upwellings, removal of one species likely has less The sea otter, at the top of the food web, acts as a “keystone discernable effects. But even open ocean systems can see dra- species” in the community. Keystone species are ones that matic changes to communities as a result of disturbance – for have, for various reasons, a substantial effect—disproportion- example, “trophic mining,” in which industrial fisheries re- ate to their numbers—on the rest of the community. Because move whole swaths of a trophic level and change the energet- they lack the blubber of other marine mammals, individual ics of the entire community (Pauly et al., 1998). sea otters need to consume a huge amount of food each day to stay warm and healthy. While a population of otters may Understanding why populations decline or why natural com- eat many things, sea urchins are their favorite prey. Since sea munities are disrupted is a critical facet of conservation. With urchins can have major effects on other species in the com- well-studied ecosystems like coral reefs and kelp forests, the munity, otter predation on them exerts a controlling influence effects of perturbation can be anticipated. But even with well- on the ecosystem. When otters are removed from the com- studied communities, questions remain. And many, many eco- munity, or their numbers are diminished, urchin barrens can logical communities are not well studied at all. result, where urchins graze down everything including the kelp that provides the foundation for the other species to live Populations decline for a variety of reasons, and ecologists (this effect is described in the Introduction to Marine Conserva- have debated the processes determining the distribution and tion Biology exercise; students are asked to predict what the abundance of individuals within populations. The debate in- effect of sea otter removal might be). cludes disputes about the relative roles of density independent and dependent factors, the importance of interspecific and Predator/prey relations are thus important to understanding intraspecific competition, predation, parasites, and mutualistic how communities of organisms are structured, and how pop- relations. Dayton (2003) suggests the following list as a small ulations of those organisms are maintained. Competition is sample of some of basic issues that need to be addressed in also important, though probably a less dominant force in most marine conservation biology. marine communities. But impacts on community ecology are not only the result of perturbations involving predators – they Cumulative effects: can be felt with the removal of herbivores (or grazers) as well. •How much is too much? What defines limits and thresh- In a recent study on coral reef community ecology in the olds?

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS 23

•What describes species vulnerability? Marine Resource Use and Conservation •Are some species redundant and expendable? •Can cumulative impacts of human perturbations be Marine Resource Use predicted? Coastal ecosystems are among the most productive, yet high- Ecosystem or habitat stability and recoverability: ly threatened systems in the world. They comprise heavily •How do we define and measure stress in multispecies sys- used coastal lands, areas where freshwater and saltwater mix, tems? and nearshore marine areas. These ecosystems produce dis- •How do we define habitat or ecosystem health? proportionately more services relating to human well-being •Why do systems collapse? What are the thresholds? than most other systems, even those encompassing larger total •What are the processes that maintain stability? areas. At the same time, these ecosystems are experiencing •What are the processes that define recoverability? some of the most rapid environmental change: almost half of the world’s mangroves have been lost or converted, and ap- Trend analysis: proximately 27% of coral reefs have been destroyed globally •How do we differentiate human induced-trends from in the last few decades. Coastal wetland loss in some places has natural trends? reached 20% annually (MA, 2005b). •What determines whether trends are general or peculiar to particular systems? Coastal areas are experiencing growing population and ex- •What spatial and temporal scales are necessary for such ploitation pressures; nearly 40% of the world population lives trend analysis? in this thin fringe of land (MA, 2005b). Demographic trends •How can society acquire trend data from already pe- suggest coastal populations are rapidly increasingly, mostly turbed systems? through migration, increased fertility, and tourist visitation to these areas. Population densities on the coasts are nearly Restoration Ecology: three times that of inland areas. Communities and industries •How to define the desired state? increasingly exploit fisheries, timber, fuelwood, construction •What are realistic goals? How are they determined? materials, oil, natural gas, sand and strategic minerals, and •How should we manipulate successional processes that genetic resources. Additionally, demand on coastal areas for are little understood? shipping, waste disposal, military and security uses, recreation, •What are the most efficient means of restoration? aquaculture, and even habitation are increasing.

This extensive list of research questions demonstrates how Shoreline communities aggregate near those types of coast- little we actually know about marine community ecology, al systems that provide the most ecosystem services (MA, and how far behind the study of terrestrial ecology marine 2005b). These subtypes are also the most vulnerable. Within science lags. In some sense conservation is hindered by these the coastal population, 71% live within 50 km of estuaries. In gaps in knowledge and most management focuses on the sim- tropical regions, settlements are concentrated near mangroves plest impacts. But innovative new management measures do and coral reefs. These habitats provide protein to a large pro- allow applied information to be gained quickly through the portion of the human coastal populations in some countries. process of adaptive management – and these approaches help Coastal capture fisheries yields are estimated to be worth a overcome information constraints. Marine conservation will minimum of USD 34 billion annually. Marine ecosystems be greatly aided in coming years if applied research is directed provide other resources as well: building materials (e.g., sand, at solving these basic questions. coral), ores, and energy (hydrocarbons, thermal energy, etc.).

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS 24

Marine systems also provide pharmaceuticals, and are highly communities of subsistence, and are causing increasing con- valued for recreational, spiritual, and cultural reasons. flicts, especially in Asia and Africa (MA, 2005c). Demands for coastal aquaculture have been on the rise, partly in response Sub-national sociological data suggest that people living in to declining capture fisheries. The doubling of aquaculture coastal areas experience higher well-being than those living production in the last 10 years, however, has also driven habi- in inland areas. The acute vulnerability of these ecosystems to tat loss, overexploitation of fisheries for fishmeal and fish oil, degradation, however, puts these inhabitants at greater relative and pollution. Over-exploitation of other resources, such as risk (MA, 2005b). The world’s wealthiest populations occur mangrove for fuel wood, sand for construction material, sea- primarily in coastal areas (per capita income being four times weeds for consumption, etc., also often undermine the eco- higher in coastal areas than inland). It is thought that life ex- logical functioning of these systems. pectancy is higher, while infant mortality is lower, in coastal regions. However, many coastal communities are politically The greatest threat to coastal systems is development-related loss of and economically marginalized, and do not derive the eco- habitats and services. Many areas of the coast are degraded or nomic benefits from these areas. Wealth disparity has led to altered, such that humans are facing increasing coastal erosion the limitation of access to resources for many of these com- and flooding, declining water quality, and increasing health munities. Access issues have in turn led to increased conflict, risks. Port development, urbanization, resort establishment, such as between small-scale artisanal fishers, and large-scale aquaculture, and industrialization often involve destruction of commercial fishing enterprises. Regime shifts and habitat coastal forests, wetlands, coral reefs, and other habitats. Histor- loss have led to irreversible changes in many coastal habitats ic settlement patterns have resulted in centers of urbanization and losses in some ecosystem services. Finally, many degraded near ecologically important coastal habitats. About 58% of the coastal systems are near thresholds for healthy functioning, and world’s major reefs occur within 50 km of major urban cen- they are simultaneously vulnerable to major impacts from sea ters of 100,000 people or more, while 64% of all mangrove level rise, erosion, and storm events. This suggests that coastal forests and 62% of all major estuaries occur near such urban populations are at risk of having their relatively high levels of centers. Dredging, reclamation, engineering works (beach ar- human well-being severely compromised. moring, causeways, bridges, etc.) and some fishing practices also account for widespread, usually irreversible, destruction Threats to Marine Ecosystems and of coastal habitats (MA, 2005b). Biodiversity Degradation is also a severe problem, since pressures within General coastal zones are growing and these areas are also the downstream recipients of negative impacts of land use. Freshwater Human pressures on coastal resources are compromising diversion from estuaries has meant significant losses of water many of the ecosystem services crucial to the well-being of and sediment delivery (30% decrease worldwide, with re- shoreline economies and peoples. While the ocean comprises gional variations) to nursery areas and fishing grounds (MA, nearly three-quarters of the Earth’s surface area, it accounts 2005b). The global average for nitrogen loading has doubled for nearly 99% of its habitable volume. Thus, disruptions within the last century. This has made coastal areas the most of marine and coastal ecosystem services have global con- highly chemically altered ecosystems in the world, with re- sequences. Coastal fisheries have depleted stocks of finfish, sulting eutrophication that drives coral reef regime shifts and crustaceans, and mollusks in all regions (MA, 2005b). Illegal other irreversible ecosystem changes. Nearly half of the global and destructive fisheries often cause habitat damage as well as population living along the shore has no access to sanitation, over-exploitation. Large scale coastal fisheries deprive shore and thus faces decreasing ecosystem services and increasing

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS 25

risks of disease (UNEP, 2002). Mining and other industries thresholds and increase the non-linearity of response (thus cause heavy metal and other toxic pollution. Harmful algal decreasing the predictability of environmental change) (MA, blooms and other pathogens, which affect the health of both 2005a). humans and marine organisms, are on the rise. This can partly be attributed to decreased water quality. Invasions of alien In addition to the proximate drivers, indirect drivers are be- species have already altered marine and coastal ecosystems, hind each of these impacts. Population growth is said to be threatening ecosystem services. the main indirect driver behind all environmental change today. The link between sheer population number and environ- The health of coastal systems and their ability to provide highly val- mental quality is not clear cut, however. Some authors argue ued services is intimately linked to that of adjacent marine, freshwater that a direct link exists between the number of people and and terrestrial systems, and vice versa. Land-based sources of pol- the quality of the environment or loss of diversity, irregardless lutants are delivered via rivers, from run-off, and through at- of consumption patterns (McKee et al., 2004). Others argue mospheric deposition. These indirect sources account for the that the number of households is better correlated to the en- large majority (77%) of pollutants (MA, 2005b). In some ar- vironmental impact or ecological footprint left by humans (Liu eas, pollution in coastal zones contaminates groundwater; this et al., 2003). In the coastal zone, however, neither population is a particular threat in drylands (MA, 2005b). Another link- numbers nor household numbers tell the full story. Patterns age occurs between expanding desertification and pollution of consumption and other human behaviors greatly influence of coral reef ecosystems caused by airborne dust. Destruction the ecological footprint left by communities, and migration of coastal wetlands has similarly been implicated in crop fail- and its effects often spell the difference between sustainable ures due to decreased coastal buffering leading to freezing in and unsustainable use (Curran and Agardy, 2002; Creel, 2003). inland areas. Local resource use and migration patterns are also affected by local and international markets. Though habitat conversion is the main driver behind coastal biodiversity loss, overexploitation of resources and, on conti- Habitat Loss and Degradation nental shelves, fisheries-related habitat destruction, degradation driven by pollution, invasive species, and climate change The most serious consequences of biodiversity loss occur when changes play major roles. Trophic cascades and trophic mining result are irreversible: e.g. habitat loss (especially complex habitats), species from overexploitation of fishery resources. This leads to bio- extinction, population extirpation, regime shifts. The most impor- diversity losses at the genetic, population, and even species tant driver behind these large scale impacts on biodiversity is levels. Marine ecosystems are less able to provide important land conversion (including coastal/marine habitat loss). How- ecosystem services (especially provisioning services) and often ever, the main drivers behind biodiversity loss are different in are less resilient as a result (MA, 2005b). Many of these im- various ecosystems. The risks of abrupt/non-linear changes pacts create negative synergies, in which multiple and cumu- in species composition and the corresponding risks of abrupt lative impacts cause greater change to ecosystems and services or non-linear changes in ecological systems vary by species than the sum of individual impacts would predict. At the and ecosystem. Although natural systems contain significant same time, all ecosystems and the biodiversity they support redundancy in terms of ecological roles that species play in are subject to multiple and cumulative impacts, both natural providing ecosystem services, there is no doubt that major de- and anthropogenic. Some ecosystems face greater numbers creases in species diversity (and thus the complexity of inter- of threats than others, particularly those that support a wide actions between species) lead to potentially unstable, though variety of uses/services (e.g. coastal ecosystems, islands). One often productive, ecosystems. Removal of species can cause effect of multiple impacts occurring simultaneously is to alter cascading effects that alter productivity at various trophic lev-

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS 26

els. Such cascading effects are most acute when keystone thresholds for all of the species that create and maintain the predators are removed (see Finke and Denno, 2004 on preda- structure (Dayton, 2003). tor diversity dampening trophic cascades, for example). There is now strong evidence of fisheries effects on seafloor While the threat of greatest magnitude to coastal systems is communities that have important ramifications for ecosystem development-related conversion of coastal habitats, degrada- function and resilience. Given the magnitude of disturbance tion is a severe problem for biodiversity, since pressures within by trawling and dredging and the extension of fishing effort coastal zones are growing and because coastal zones are the into deeper, more sensitive benthic communities, this type of downstream recipients of negative impacts of land use. Fresh- human disturbance is one of the most significant threats to water diversion from estuaries has meant catastrophic losses biodiversity and the provision of ecosystem services (Thrush of water and sediment delivery (30% decrease worldwide) to and Dayton, 2002). nursery areas and fishing grounds. At the same time, external inputs lead to loss of biodiversity, reduction of ecosystem ser- Invasive Species (Including Pathogenic Diseases) vices, and declines in human well-being, especially in coastal communities. Invasion of coastal and marine areas by non-indigenous or alien species is a major threat to marine biodiversity and ecosystem function- Resource Extraction ing, much as invasions are causing major ecological changes on land. Altering soft bottom habitat to hard bottom in the process Fishing and other extraction activities affect the stocks of liv- often affects estuaries indirectly by creating conditions for ing and non-living resources, the things that feed or are fed new assemblages of species, and facilitating range expansions upon by those resources, and the habitat that supports marine of invasive species (Ruiz and Crooks, 2001). The resulting life. In general, resource removal is detrimental when the ecosystems may have losses in some ecosystem services and amount of removal is greater than the capacity for the liv- biodiversity. In New Zealand invasive species have displaced ing resource to replenish itself (known as over-exploitation), commercially important mussel beds, resulting in significant when the resource being removed has a key role to play in economic losses for many mussel farmers (NOAA News On- community ecology, or when the method of removal is de- line, 2003). structive. In essence, this boils down to three questions: 1) how much removal is sustainable?; 2) which resources can be Estuarine systems are among the most invaded ecosystems removed sustainably?; and 3) how can resources be removed in the world, with exotic introduced species causing major sustainably? (i.e. by what methods?). ecological changes (Carlton, 1989, 1996). Often introduced organisms change the structure of coastal habitat by physi- While it would appear that significant concerns about fisher- cally displacing native vegetation (Harris and Tyrrell, 2001; ies impacts on the marine environment exist, most concern Grosholz, 2002; Murray et al., 2004). For example, San Fran- over the environmental effects of fishing has focused on near- cisco Bay (U.S.A.) has over 210 invasive species, with one shore habitats. In fact, the vast scope of ecological destruction new species established every 14 weeks between 1961 and of the full suite of marine habitats has only recently been doc- 1995 (Cohen and Carlton, 1995, 1998). Most of these bio- umented. The removal of small-scale heterogeneity associated invaders were borne by ballast water of large ships or occur with the homogenization of habitats is an important cause as a result of fishing activities (Carlton, 2001). The ecologi- of the loss of biodiversity in many marine systems (Dayton, cal consequences of the invasions include: habitat loss and 2003). And restoration of the system depends upon an un- alteration; altered water flow and food webs; the creation of derstanding of structure in time and space, and of biological novel and unnatural habitats subsequently colonized by oth-

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS 27

er exotic species; abnormally effective filtration of the water climate change, including increased precipitation in some column; hybridization with native species; highly destructive areas, abrupt warming at the poles, and increased frequency predators; and introductions of pathogens and disease (Ruiz and intensity of storm events, would affect oceanic circula- et al., 1997; Bax et al., 2003). tion (perhaps even leading to the collapse of thermohaline circulation) and currents, and the ability of organisms to live Climate Change or reproduce.

The geographically largest scale impacts to coastal systems are caused Most Threatened Areas by global climate change, and since rates of warming are generally expected to increase in the near future, projected climate change-related Island systems are especially sensitive to disturbances, and impacts are also expected to rise (IPCC, 2003). Warming of the island biota particularly vulnerable to extinction, primarily world’s seas degrades coastal ecosystems and affects species in driven by ecological changes wrought by invasive species. many ways: by changing relative sea level faster than most bi- Many islands serve as important biological refugia for species omes can adapt; by stressing temperature-sensitive organisms that are either extinct or threatened on nearby continental such as corals and causing their death or morbidity (in corals landmasses. The habitat destruction and biodiversity loss on this is most often evidenced by coral bleaching); by changing islands may therefore have more immediate and serious re- current patterns and thus interfering with important physio- percussions than on continental systems. With growing popu- biotic processes; and by causing increased incidence of patho- lation and exploitation pressures, the impact on some island gen transmission (MA, 2005b). Coral reefs may be the most systems has exceeded the critical point. Invasive species are vulnerable, having already evidenced rapid change, and some one of the most significant drivers of environmental change projections predict the loss of all reef ecosystems this century to islands over the world, and oceanic islands are more suc- (Hughes et al., 2003). Global warming also changes the tem- cessfully invaded by vertebrates compared to corresponding perature and salinity of estuary and nearshore habitats, making continental areas. them inhospitable to species with narrow temperature toler- ances. Warming can also exacerbate the problem of eutrophi- Nearshore areas are particularly vulnerable to anthropogenic cation, leading to algal overgrowth, fish kills, and dead zones threats. The destruction of the natural watershed often results (Burke et al., 2001). Finally, warming is expected to further in the loss of most of the attributes of estuarine habitat, for increase the transmission rates of pathogens and hasten the instance. Poor management of watersheds, including poor spread of many forms of human and non-human disease. grazing practices that destroy natural riparian habitats, results in floods and burial of the natural habitats under silt and en- Climate change-related sea level rise will cause continued in- riched sediment. Often these impacts combine with severe undation of low-lying areas, especially in areas where natural nutrient loading, causing large coastal areas to become anoxic. buffers have been removed (Church et al., 2001). Sea level An extreme example is the massive (up to 15,000 km2) dead rise is due to thermal expansion of ocean waters and melting zone in the Gulf of Mexico (Turner and Rabalais, 1994). Ur- of land-based ice, and both expansion and ice melts are ex- banization of watersheds interrupts the flow of both essential pected to increase (IPCC, 2003). In most if not all cases, glob- fresh water and nutrients. Nutrient loading and eutrophica- al climate change impacts act in negative synergy with other tion result in prolonged ecological degradation, as algae take threats to marine organisms, and can be the factor sending over bottom habitats and the water column so that the entire ecosystems over the threshold levels for stability and produc- ecosystem is altered (Levin et al., 2001). tivity. In limited cases, new habitats may be created. Changes in weather patterns modeled in some extreme scenarios of Coral reefs and the ecosystem services they provide are espe-

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS 28

cially threatened by anthropogenic forces (Birkeland, 2004). 3) restoration; 4) integrated coastal management; and 5) inter- Ecosystem services provided by coral reefs include habitat national treaties and agreements. These five major themes are and nurseries for fish, nutrient cycling and carbon fixing in presented not by order of importance but rather by the scale nutrient-poor environments, wave buffering and sediment at which they are practiced, beginning with the smallest geo- stabilization, and a number of cultural ecosystem services. graphical scale and extending to the largest. Truly effective These ecosystem services associated with coral reefs can only marine conservation requires that these sorts of initiatives be be maintained if: 1) the ecosystem remains intact, and 2) the tied together in a holistic manner, so that not only individual interaction between corals and their obligate symbiotic algae sites are protected but the entire context in which such sites is preserved. lie is protected as well. In many instances, however, a mismatch of scales occurs such that rather than complementing Great attention has been paid to the decline in species diver- one another, these sorts of methods can impede one another sity in terrestrial ecosystems, however it is apparent that there – especially when marine conservation planning is focused are substantial changes in diversity in deep ocean benthos only at a particular scale and not the hierarchy of scales that is – albeit changes that may not be so readily detected (Day- reality (Agardy, 2005). ton, 2003). Direct killing and habitat loss are primary factors responsible for the global decline in diversity. Most bottom Spatial Management Through Zoning and Marine habitats are characterized by biological construction in which Protected Areas the organisms provide structure critical to many other parts of the ecosystem. Examples include reefs of mussels, oysters, Individual sites recognized for their valuable services are sponges, corals (including some 700 species of deep-water sometimes protected through zoning regulations and other corals that may tower more than 40 m above the sea floor), spatial management interventions, such as marine protected kelp forests, sea grass meadows, and even large single-celled areas (MPAs) (NRC, 2001). Such protected areas may be foraminiferans, all of which fill important ecological roles with- small fisheries reserves in which resource extraction is pro- in the community (Levin et al., 1986; Rogers, 1999). These hibited, or they may occur in the context of larger multiple- roles include filtering the seawater and affecting its flow. The use areas. Increasingly, marine protected areas are being es- biological structure also serves to retain water masses with lar- tablished in networks in order to safeguard key areas of the vae, and it furnishes critical habitats and predator protection. coastal and marine environment over a geographically large The architectural complexity supports a diverse association area (Agardy, 1999; Murray et al., 1999; Pauly et al., 2002). A of feedback loops that define the biological complexity of prime example of this is the network of reserves encompassed seafloor processes. These important ecological roles are as yet by the newly re-zoned Great Barrier Reef Marine Park in very poorly understood (Dayton, 2003). Physical disturbance Australia (Day, 2002). by fishing, mining, etc. can thus significantly impact habitat, species diversity, and interlinked ecological processes. In order for marine protected areas to succeed in meeting the objectives of conserving habitats and protecting fisheries and Methods to Conserve Marine Biodiversity biodiversity, management seeks to address all relevant direct threats. In most habitats, these threats are multiple and cumu- There are many methods used in marine conservation; in- lative over time. Thus, protected areas that address only one deed, the toolbox is full, though seldom fully utilized. How- of these will usually fail to conserve the ecosystem or habitats ever, many of these tools can be discussed in the context of and the services they provide. five major kinds of marine management: 1) spatial management through marine protected areas; 2) fisheries management; Marine and coastal protected areas already dot the coasts of

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS 29

all the world’s areas, and the numbers of protected areas con- or species does not necessarily lead to conservation of the tinue to increase. The last official count of coastal and marine wider community or biodiversity of the region. protected areas in 2003 yielded 4,116 (Spalding et al., 2003). This represents a marked increase over the 1,308 listed in Resource use that is managed in a way that considers the 1995 (Kelleher et al., 1995). It is, however, a significant un- impacts that resource removal has on all linked ecosystems derestimate because unconventional protected areas that do and human well-being has proven to be more effective than not fit the IUCN categories for protected areas are typically sectoral or single-species management (Kay and Alder, 2005). not counted (see the Marine Protected Areas and MPA Networks Fisheries agencies and conservationists are promoting eco- module). By far the bulk of these protected areas occur in the system-based fisheries management. This is management coastal zone, and many include both terrestrial and aquatic that looks at multispecies interactions and the entire chain components (MA, 2005b). Even with the large number of of habitats these linked organisms need in order to survive individual sites, however, coverage accounts for less than 0.5% and reproduce (Agardy, 2002). Due to the linkages between of the world’s oceans. Many marine protected areas occur in marine fisheries production and coastal ecosystem condition, relatively close proximity to human settlements. In fact, near- the protection of coastal habitats figures very prominently in ly ten percent of the global human population lives within ecosystem-based fisheries management (Pauly et al., 2002). 50 kilometers of a marine protected area, and over 25% of However, truly holistic integrated management also requires the worldwide coastal population lives within 50 kilometers complementary watershed management and land use plan- of a marine protected area (MA, 2005b). Management ef- ning to ensure that negative impacts do not reach these areas fectiveness of most MPAs remains questionable, and many of from outside the coastal realm. these have no operational management or enforced legislation at all. It is well established that marine protected area Implementation of ecosystem-based management (EBM) tools are not being used to their fullest potential anywhere in for fisheries requires a multi-pronged approach. Dinesen and the world (Agardy et al., 2003). Gribble (2005) explore the dual roles of modeling and policy development in enhancing EBM for Queensland-managed Fisheries Management fisheries in Australia. ECOPATH software is used to simulate temporal and spatial reactions to commercial fishing and the Management of living marine resource use has been prac- imposition of a “no take” zone within an MPA. The addition ticed for several centuries. Conventional fisheries manage- of spatially explicit habitat data to the equilibrium GBR eco- ment relies on fish population dynamics models that suggest system model significantly buffered the predicted volatility maximum sustainable yield (MSY) for a particular stock. This in trophic guild biomass, by providing de facto spatial refugia information is then used to identify appropriate manage- from fishing pressure. The simulations showed that additional ment regimes such as restrictions on catch (quotas, size limits, protected “no take” zones must be of adequate size to allow age class restrictions, etc.), gear, and harvest time (duration for “edge effects” caused by illegal fishing, particularly if sited of fishing season). Fisheries managers also look to tempo- in remote areas. Fishing tended to concentrate on the borders rary, seasonal, rotating, or permanent MPAs as a way to target of the “no take” zone, which produced “gauntlet” effects to sustainability (MA, 2005c). Determining where to establish the movement of some groups. Vulnerable species did bet- fisheries reserves requires an understanding of life histories ter within “no take” MPA areas, but scavenger/opportunistic and determination of essential fish habitat (EFH). These spa- species did worse. tial management techniques are most successful in fisheries targeting species whose ecology is well known (Sale et al., Ecosystem-based fisheries management is currently de rigeur, 2005). However, even effective management of a single stock even though some fisheries managers profess uncertainty

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS 30

about what the term actually means, and in what ways em- these ecosystems are defined by physical oceanography and bracing the concept will change day-to-day operations of fisheries data, and not by other considerations of biodiver- fisheries agencies (Lubchenco, 1998). Nonetheless, there are sity. The LME concept was originally applied in the fisher- parts of the world where management is moving away from ies context under CCAMLR to take into account predator/ single species or even small-scale multi-species strategies to prey relationships and environmental factors affecting target broader marine management. Many of these initiatives began stocks. Thus, Antarctica became the first site of a truly ecosys- as a result of regional fisheries agreements (Griffis and Kim- tem-based approach to fisheries management, and the target ball, 1996). A literature has begun to emerge on ecosystem- area was defined by the limits of the Antarctic LME. Several based fisheries management (e.g., Sinclair and Valdimaarson, recent international instruments refer to LMEs. In addition, 2003). the geographic units serve as the basis for some global as- sessments, such as the UNEP’s Global International Waters Arguably, the best example of ecosystem-based marine man- Assessment (GIWA; www.giwa.org). However, in many parts agement is the Convention on Conservation of Antarctic of the world, the political constituency for nations to cooper- Marine Living Resources (CCAMLR). Many regional fish- ate to conserve the large scale ecosystems and marine species eries agreements are delimited by the boundaries of large ma- they share is limited, though this situation may be improving rine ecosystems (LMEs). These are regions of ocean space (Wang, 2004; see the Marine Protected Areas and MPA Networks that extend from inshore to the seaward boundaries of con- module). tinental shelves and seaward margins of coastal current systems (Kimball, 2001). There are 64 LMEs globally, averaging Restoration 200,000 square kilometers, and characterized by distinct bathymetry, hydrology, productivity, and trophically-dependent Some key coastal habitats, such as mangrove forests, marshes, populations (Sherman, 1993; Wang, 2004). The LME concept and seagrass meadows, can be, and are being, restored once originated from fisheries management. Even today most of degraded. The science of mangrove restoration is relatively advanced. This is especially the case when natural species diversity is low, and replanting a few species can restore ecosystems and most services quickly (Kaly and Jones, 1998). Marshlands are also relatively easily restored, as long as major alterations to hydrology have not taken place. Such initiatives are risky, however, since it has yet to be shown that the full range of ecosystem services can be supported by arti- ficially reconstructed wetlands (NRC, 1992; Moberg and Ronnback, 2003). Coral reef transplantation, though technologically possible, can only be practiced at a small scale, and has had limited success (Moberg and Ron- Green moray eel (Source: K. Frey) nback, 2003). Furthermore, the costs

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS 31

can be enormous, as the USD 7.8 billion price tag for the res- ordinated pollution controls, development restrictions, fisher- toration of the Everglades cord-grass system in Florida (US) ies management, and scientific research. attests. In fact, most full-scale restoration (habitat reconstruc- tion) is practiced in highly developed countries that are able Significant strides have been made in coastal management in to finance the high costs over the long time frames needed. the last few decades, in both the developed and developing world. Many of the earth’s 123 coastal countries have coastal Restoration and subsequent management should be based on management plans and legislation, and new governance ar- understanding the sources of propagules of the target species. rangements and regulations are being developed every year Understanding propagule sources, however, requires under- (Burke et al., 2001). In 1993, it was estimated that there standing the strong interactions (Sala and Graham, 2002) and were 142 coastal management initiatives outside the U.S.A. definition of target species in most urgent need of manage- and 20 international efforts (Sorensen, 1993). By 2000, there ment. There is a pressing need to better understand the Allee were a total of 447 initiatives worldwide, including 41 at the effect (discussed above) in which sources of propagules, and global level (Hildebrand and Sorensen, 2001). This dramatic the thresholds in their respective spawning aggregations, are increase in activity was attributed both to new plans imple- defined. In addition, it is important to distinguish between mented since 1993, and to the improved ability to find rel- larval nurseries and sinks, and establish the relative abundanc- evant information using the Internet (Kay and Alder, 2005). es of each. A clear understanding of successional processes is The latest survey estimates that there are a total of 698 coastal also important. management initiatives operating in 145 nations or semi-sov- ereign states, including 76 at the international level (Sorensen, Integrated Coastal Zone Management 2002).

Complex problems require comprehensive solutions and an Yet even countries with well-developed coastal zone plans integrated management response is needed to conserve most that have been in place for decades struggle with over-ex- aspects of biodiversity, especially at the ecosystem level. Sec- ploitation of resources, user conflict, habitat loss, and indi- toral approaches have been proven to have shortcomings in rect degradation of ecosystems. These may involve activities management of complex issues such as biodiversity. In marine occurring sometimes hundreds of kilometers away from the environments, connectivity over large geographic distances focal area. Management has not kept pace with degradation, requires a melding of a top-down management approach as the number of interventions worldwide has only increased with the more local and national level approaches typical to two or threefold over the last decade. In the same time period, most biodiversity conservation. degradation of many habitats, such as coral reefs and mangroves, has increased significantly more (Kay and Alder, 2005). Integrated management of watersheds, land use planning, and There has been far too much emphasis on process rather than impact assessment are key to protecting coastal ecosystems achieving results, and stakeholder participation is often seen (Sorenson, 1997). For this reason, tackling the issues of loss as an end in itself instead of a critical step in a larger, more and degradation of these areas by addressing single threats has complex process. not proven effective in the past. The holistic approach, look- ing at how human activities affect coastal ecosystems, iden- Regional and International Agreements/Treaties tification of key threats, and implementation of management that is integrated across all sectors, is a relatively new focus. Many environmental issues, such as pollution, climate change, This is likely to produce much more effective decision-mak- protection of marine and freshwater resources, and biodiver- ing. Successful management of these crucial areas means co- sity conservation, are large scale topics that require multi-na-

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS 32

tional governmental actions to address them. This is particu- tional law remains a sticking point, and too often national larly true in the marine context. When resources are shared laws are not harmonized to allow international agreement by more than one country, or consequences result from geo- obligations to be carried out. graphically removed actions, national action alone cannot suf- fice (Kimball, 2001). Most marine species cross boundaries Global treaties that include all coastal and some riparian na- of individual countries, and the regulation of these resources tions are crucial in addressing certain marine conservation is beyond the control and responsibility of individual na- issues. However, equally important marine agreements exist tions. In addition, the oceans contain vast areas that do not on the regional scale. Most important among these are the fall under the jurisdiction of any nation. These “high seas” Regional Seas Agreements overseen by the United Nations are thus a global commons that cannot be addressed in any way Environment Programme (UNEP) and various regional fish- other than international cooperation and global agreements eries agreements. Regional fisheries agreements such as the (see The Pelagos Sanctuary for Mediterranean Marine Mammals International Convention on the Conservation of Atlantic case study). Such treaties and other agreements are the most Tunas (ICCAT) allow countries to cooperate in managing frequent means of addressing the conservation of the ‘global shared fish stocks, as well as allowing fisheries management to commons’ and worldwide environmental problems. They fos- become more holistic and thus effective by promoting eco- ter a worldwide conservation ethic where the world’s nations system-based management approaches. strive to conserve marine biodiversity and the environment by working together on global solutions (see the International Constraints To Effective Marine Treaties for Marine Conservation and Management module). Conservation

International treaties provide a legal framework for marine Just as marine ecosystems are complex, so do political, social conservation action, resource regulation, and scientific re- and economic systems exhibit complex non-linear dynamics search on a broad scale. Such agreements exist at various with thresholds. Social systems are constantly in flux – per- scales, depending on the nature of the issue and the practi- haps even more so than natural ones. Abrupt changes can calities of fostering cooperation among countries. Some are occur in political (e.g., elections or revolutions), social (e.g., global, involving virtually all nations; others are formulated changes in fashions) or economic systems (e.g., technological with only those parties having coastal jurisdictions, while still changes leading to changes in what is produced or how it is others are regional and involve only countries bordering a produced). For example, an advance in fishing technology particular ocean basin, semi-enclosed sea, or region. Thus, from dugout canoes to trawlers with long-line nets and GPS these treaties can be bilateral (between two countries or ‘par- can cause massive changes in rates of resource exploitation. ties’) or multilateral (between multiple countries). However, These jumps in exploitation rates often pass the threshold for regardless of scale, these agreements legally mandate interna- sustainability, and may result in crashes in fish stocks and oth- tional cooperation to address complex environmental issues, er profound alterations in marine ecosystems. These impacts aiming to promote sustainable utilization and protection of may also be irreversible, since a return to previous low tech shared natural resources. They form the rules of conduct or methods is unlikely, and fish stocks may be unable to recover behavior agreed upon by the signatory states to take actions even if fishing pressure is subsequently reduced. that address a conservation and/or environmental issue. In the twentieth century, it has been suggested that environmental Inertia is a fundamental characteristic of socio-economic and treaties are the best means of making law in our diverse world natural systems. There is typically a time lag between a pertur- (see the International Treaties for Marine Conservation and Man- bation to the system and the complete eventual effects. For agement module). But the question of who enforces interna- example, a reduction in habitat may not result in immediate

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS 33

loss of species in a region. Population levels, however, will fall can trigger dramatic effects, often with large losses in ecosys- over time in response to the reduction in habitat. Eventually tem services. For these reasons, conservation is best achieved the population reaches a level where it is no longer sustain- by focusing on conserving or restoring the composition of able and the species will suffer local extinction. This may oc- communities, rather than simply maximizing species numbers. cur many decades after habitat reduction (MA, 2005a). Particularly important is the preservation of the complex interactions among species, including links between pelagic and Socio-economic institutions also illustrate considerable iner- benthic organisms, keystone species, ecosystem engineers, and tia. Culture and tradition may make societies reluctant to natural enemies of pests and human-disease vectors. change practices, even in the face of altered environmental circumstances. Fixed investments in plants, equipment, and As conservationists, we must come to terms with the fact infrastructure make fundamental changes in production or that considerable uncertainty exists in our understanding of consumption costly. New conditions may take place over what is in the oceans, how things interact, and how humans time as fixed investments wear out and are replaced with new, use and impact the ocean environment and biodiversity. This better adapted investment. In many regions, population pres- uncertainty is sometimes held up as an excuse for inaction sures on limited land and water resources, government poli- – something that civil societies urge decision makers to resist. cies impeding flexibility and adaptation, or limited access to But the uncertainty can also be harnessed, in a sense, for con- information or financial resources make adaptation difficult servation, by creating the conditions that allow conservation- or slow. ists to promote the precautionary principle. This principle essentially states that in the face of uncertainty, we should err on Anticipating major changes is complicated by lags in respons- the side of conservation until better information is gained. es, complex feedbacks between socio-economic and ecological systems, and the difficulty of predicting thresholds prior However, there is much political resistance to invoking the to such benchmarks being passed. There are a number of precautionary principle, especially in resource management intrinsic characteristics of ecosystems and of science that con- circles that are time-bound by traditional management (es- tribute to this. Ecological lag times often mean that responses pecially fisheries management). Another constraint is that to changes in biodiversity do not occur immediately; multiple though the need to establish management regimes that are impacts (especially the addition of climate change to the mix designed to further our ecological and sociological under- of forcing functions) can cause alterations in thresholds; and standing is well accepted, developing such adaptive manage- monitoring methods are often inadequate due to poor choice ment methods is difficult, time consuming, and potentially of indicators, inappropriate periodicity of monitoring, and in- costly. frequent analysis of results (MA, 2005a). Therefore, incomplete ecological understanding, and corol- A mismatch exists between the dynamics of natural systems lary incomplete sociological understanding, can be a major and human responses to those changes. Inertia and lag times constraint in effective conservation. Other constraints in- in both natural and social arenas complicate the ability of hu- clude lack of funding for research to bolster that understand- mans to anticipate and develop adaptation strategies to cope ing and also funding to undertake monitoring and enforce- with change. The result of our current inadequacies in un- ment of regulations. Perhaps the biggest constraint of all is derstanding is increasing numbers of “ecological surprises” lack of political will, based in part in the misconception that brought about by voluntary or accidental species introduc- the oceans are so large that humans could not possibly impact tions or removals. These illustrate how initially small changes them, and in part in the sense that open access must be pre- in species richness (i.e. often just the addition of one species) served in the oceans since they are indeed a global commons

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS 34

(Agardy, 1997). making generalizations from a few well-known systems like tropical coral reefs is risky, given the structural and functional Conclusions diversity that is exhibited by different portions of the oceans and coastal areas. Given that we cannot wait for perfect Ecological systems are extraordinarily complex and confus- ecological understanding, however, marine conservationists ing. The populations that compose the systems often respond would be best served by promoting adaptive management to environmental factors that are as yet virtually unknown. Yet wherever possible, so we might learn as we go along. Adap- they must be studied with the classical scientific techniques tive management frameworks not only position us for more of simplification, analysis, and synthesis, and testing theory effective management, but also increase the speed with which remains the cornerstone of science (Dayton, 2003). A trap critical new knowledge is gained. exists, however, since bad assumptions can be quantitative and precise, esthetically pleasing, and appear heuristically useful, Finally, integrated and holistic approaches that tackle the and experiments might make the right predictions for the myriad, cumulative threats to marine systems are needed. In wrong reasons (see Dayton and Sala, 2001). order to match the scale of these large, highly interconnected and in many cases open systems, international cooperation Social systems are also extraordinarily complex. A promis- may be needed to achieve real conservation. ing new development in conservation, however, looks at the resilience of social systems as well as ecosystems (Adger et Terms of Use al., 2005). Developments such as these suggest that marine conservation seems at last able to couple human and natural Reproduction of this material is authorized by the recipient systems and better understand the interactions between the institution for non-profit/non-commercial educational use two. and distribution to students enrolled in course work at the institution. Distribution may be made by photocopying or via As in the terrestrial literature, the last century has produced a the institution’s intranet restricted to enrolled students. Re- large marine literature. But the value for application to con- cipient agrees not to make commercial use, such as, without servation of much of this literature is truncated by the limited limitation, in publications distributed by a commercial pub- appreciation of the important scales in time and space. While lisher, without the prior express written consent of AMNH. the focus on small scales is understandable for many practical reasons, arguably the most important lesson of the last several All reproduction or distribution must provide both full cita- decades is the importance to local communities of oceano- tion of the original work, and a copyright notice as follows: graphic processes operating on much larger scales in time and space. With few exceptions, there are no time-series observa- “Agardy, T. 2007. Introduction to Marine Conservation Biol- tions that allow a holistic definition of what is natural for the ogy. Synthesis. American Museum of Natural History, Lessons ocean ecosystem (Dayton, 2003). in Conservation. Available at http://ncep.amnh.org/linc.”

Some systems are now almost as well understood as terres- “Copyright 2007, by the authors of the material, with license trial systems that have been studied for centuries. Focusing for use granted to the Center for Biodiversity and Conserva- on these systems allows us to make predictions about future tion of the American Museum of Natural History. All rights condition of ecosystems and trends in populations of organ- reserved.” isms, which are in turn needed to develop effective management regimes and bring about necessary policy changes. But This material is based on work supported by the National

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS 35

Oceanic and Atmospheric Administration Undersea Research lethal arm damage in ophiuroids: A Jurassic-recent com- Program (Grant No. CMRC-03-NRDH-01-04A) parison. Marine Biology Progress Series 74:9107. Bax, N., A. Williamson, M. Aguero, E. Gonzalez, and W. Geeves. Any opinions, findings and conclusions, or recommendations 2003. Marine invasive alien species: a threat to global bio- expressed in this material are those of the authors and do diversity. Marine Policy 27(4): 313-323. not necessarily reflect the views of the American Museum of Beck, M.W., K.L. Heck, K.W. Able, D.L. Childers, D.B. Egg- Natural History or the National Oceanic and Atmospheric leston, B.M. Gillanders, B. Halpern, C.G. Hays, K. Hoshino, Administration. T.J. Minello, R.J. Orth, P.F. Sheridan, and M.R. Weinstein. 2001. The identification, conservation, and management of Literature Cited estuarine and marine nurseries for fish and invertebrates. Bioscience 51(8): 633-641. Adger, W.N., T.P. Hughes, C. Folke, S.R. Carpenter, and J. Bellwood, D.R., T.P. Hughes, C. Folke, and M. Nystrom. 2004. Rockstrom. 2005. Social-ecological resilience to coastal Confronting the coral reef crisis. Nature 429(6994): 827- disasters. Science 309:1036-1039. 833. Agardy, T. 1997. Marine Protected Areas and Ocean Conser- Birkeland, C. 2004. Ratcheting down the coral reefs. BioSci- vation. RG Landes Company and Academic Press, Austin, ence 54(11): 1021-1027. TX, USA. Bouchet, P., P. Lozouet, P. Maestrati, and V. Heros. 2002. As- Agardy, T. 1999. Creating havens for marine life. Issues in Sci- sessing the magnitude of species richness in tropical marine ence and Technology 16(1): 37-44. environments: exceptionally high number of mollusks at a Agardy, T. 2002. An environmentalist’s perspective on respon- New Caledonia site. Biological Journal of the Linnaean sible fisheries: The need for holistic approaches. Pages 65- Society 75: 421-436. 85 in M. Sinclair and G. Valdimarson, editors. Responsible Burke, L., Y. Kura, K. Kassem, C. Ravenga, M. Spalding, and D. Fisheries in the Marine Ecosystem. Food and Agriculture McAllister. 2001. Pilot Assessment of Global Ecosystems: Organization of the United Nations (FAO) and CAB In- Coastal Ecosystems. World Resources Institute (WRI), ternational, Rome, Italy, and Wallingford, UK. Washington, D.C., USA. Agardy, T. 2005. Global marine conservation policy versus site Carlton, J.T. 1989. Man’s role in changing the face of the level implementation: the mismatch of scale and its impli- oceans: biological invasions and implications for conser- cations. Marine Ecology Progress Series 300: 242-248. vation of near-shore marine environments. Conservation Agardy, T., and J. Alder. 2005. Coastal systems and coastal Biology 3:265-273. communities. Ch. 19 In Millennium Ecosystem Assess- Carlton, J.T. 1996. Marine Bioinvasions: The alteration of ma- ment, Vol. 1: Conditions and Trends. Available from www. rine ecosystems by nonindigenous species. Oceanography millenniumassessment.org 9(1):36-43. Agardy, T., P. Bridgewater, M.P. Crosby, J. Day, P.K. Dayton, R. Carlton, J.T. 2001. Introduced Species in U.S. Coastal Wa- Kenchington, D. Laffoley, P. McConney, P.A. Murray, J.E. ters: Environmental impacts and Management Priorities. Parks, and L. Peau. 2003. Dangerous targets: Differing per- Prepared for the Pew Oceans Commissions, Arlington, VA, spectives, unresolved issues, and ideological clashes regard- USA. ing marine protected areas. Aquatic Conservation: Marine Cohen, A.N., and J.T. Carlton. 1995. Nonindigenous Aquatic and Freshwater Ecosystems 13:1-15. Species in a United States Estuary: A Case Study of the Alder, J. 2003. Distribution of estuaries worldwide. Sea Around Biological Invasions of the San Francisco Bay and Delta. Us Project, UBC, Vancouver, B.C., Canada. A report for the United States Fish and Wildlife Service, Aronson, R.B. 1991. Predation, physical disturbance, and sub- Washington D.C., USA.

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS 36

Cohen, A.N., and J.T. Carlton. 1998. Accelerating invasion itat loss and degradation on fisheries. R.N. Buchsbaum, rate in a highly invaded estuary. Science 279(5350): 555- W.E. Robinson, and J. Pederson, editors. The decline of 558. fisheries resources in New England: evaluating the impac- Church, J.A., J.M. Gregory, P. Huybrechts, M. Kuhn, K. Lam- to fo overfishin, contamination, and habitat degradation. beck, M.T. Nhuan, D. Qin, and P.L. Woodworth. 2001. Massachusetts Bays Program, Massachusettes Institute of Changes in Sea Level. Pages 639-694 in J.T. Houghton, Technology Sea Grant Press, Cambridge, MA, USA. Y. Ding, D.J. Griggs, M. Noguer, P. van der Linden, X. Dai, Dinesen, Z., and N.A. Gribble. 2005. Ecosystem-based man- K. Maskell, and C.I. Johnson, eds. Climate Change (2001). agement of fisheries: Modeling and policy initiatives for The Scientific Basis. Contribution of Working Group 1 Queensland-managed fisheries. Available from http:// to the Third Assessment Report of the Intergovernmen- www.cedsign.com.au/Coast%20th%20%202004%20(CD tal Panel on Climate Change, Cambridge University Press, %20Proceedings)/pages/coastfinal00096.pdf Cambridge, UK. Duke, N.C. 1992. Mangrove Floristics and Biogeography. Creel, L. 2003. Ripple Effects: Population and Coastal Re- Pages 63-100 in A.I. Robertson and D.M. Alongi, editors. gions. Making the Link: Population Reference Bureau. Tropical Mangrove Ecosystems. American Geophysical Curran, S.R., and T. Agardy. 2002. Common property systems, Union, Washington, D.C., USA. migration and coastal ecosystems. Ambio 31(4), 303-305. Ewel, K.C., R.R. Twilley, and J.E. Ong. 1998. Different kinds Day, J.C. 2002. Zoning - lessons from the Great Barrier Reef of mangrove forests provide different goods and services. Marine Park. Ocean & Coastal Management 45(2-3): 139- Global Ecology and Biogeography 7(1): 83-94. 156. Finke, D.L., and R.F. Denno. 2004. Predator diversity damp- Dayton, P.K. 1994. Community landscape: Scale and stabil- ens trophic cascades. Nature 429(6990): 407-410. ity in hard bottom marine communities. Pages 289-332 Fonseca, M.S., W.J. Kenworthy, and G.W. Thayer. 1992. Sea- in P.S. Giller, A.G. Hildrew, and D.G. Raffaelli, editors. grass beds: nursery for coastal species. Pages 141-147 in Aquatic Ecology: Scale, pattern and process. Blackwell R.H. Stroud, editor. Stemming the Tide of Coastal Fish Press, Oxford, UK. Habitat Loss. Marine Recreational Fisheries Symposium, Dayton, P.K. 2003. The importance of the natural sciences to 7-9 March 1991, Baltimore, MD, USA. National Coalition conservation. American Naturalist 162(1): 1-13. for Marine Conservation, Savannah, GA, USA. Dayton, P.K., and E. Sala. 2001. Natural history: the sense of Food and Agriculture Organization (FAO). 2002. The state of wonder, creativity and progress in ecology. Scientifica Ma- world fisheries and aquaculture. FAO, Rome, Italy. rina 65:199-206. Gerrodette, T. 2002. Tuna-Dolphin Issue. In W. Perrin, B. Wur- Dayton P.K., M.J. Tegner, P.B. Edwards, and K.L. Riser. 1998. sig, and J.G.M. Thewissen, editors. Encyclopedia of Marine Sliding scales, ghosts, and reduced expectations in kelp for- Mammals. Academic Press, San Diego, CA, USA. est communities. Ecological Applications. 8(2): 309-322. Gray, C.A., D.J. McElligott, and R.C. Chick. 1996. Intra- and Dayton, P.K., S.F. Thursh, M.T. Agardy, and R.J. Hofman. inter-estuary differences in assemblages of fishes associated 1995. Environmental effects of marine fishing. Aquatic with shallow seagrass and bare sand. Marine and Freshwa- Conservation: Marine and Freshwater Ecosystems 5:205- ter Research 47(5): 723-735. 232. Green, E.P., and F.T. Short. 2003. World Atlas of Seagrasses. Deegan, L.A. 1993. Nutrient and energy transport between University of California Press, Berkeley, CA, USA. estuaries and coastal marine ecosystems by fish migration. Griffis, R.B., and K.W. Kimball. 1996. Ecosystem approaches Canadian Journal of Fisheries and Aquatic Sciences 50:74- to coastal and ocean stewardship. Ecological Applications 79. 6(3): 708-712. Deegan, L.A., and R.N. Buchsbaum. 2001. The effect of hab- Grosholz, E. 2002. Ecological and evolutionary consequences

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS 37

of coastal invasions. Trends in Ecology and Evolution 17 118:16-26. (1): 22-27. Johannes, R.E., L. Squire, T. Graham, Y. Sadovy, and H. Ren- Harris, L.G., and M.C. Tyrrell. 2001. Changing community guul. 1999. Spawning aggregations of Groupers (Serrani- states in the Gulf of Maine: synergism between invaders, dae) in Palau. Marine Conservation Research Series Pub- overfishing and climate change. Biological Invasions 3:9- lication No.1, The Nature Conservancy. 21. Kaly, U.L., and G.P. Jones. 1998. Mangrove restoration: A po- Hatcher, B., R. Johannes, and A. Robinson. 1989. Review of tential tool for coastal management in tropical developing the research relevant to the conservation of shallow tropi- countries. Ambio 27(8): 656-661. cal marine ecosystems. Oceanography and Marine Biology Kay, R. and J. Alder. 2005. Coastal Planning and Management. 27:337-414. 2nd edition. EF&N Spoon, London, UK. Heck, K.L.J., D.A. Nadeau, and R. Thomas. 1997. The nurs- Kelleher, G., C. Bleakley, and S. Wells. 1995. A global rep- ery role of seagrass beds. Gulf of Mexico Science 15(1): resentative system of marine protected areas. Vol. 1, Great 50-54. Barrier Reef Marine Park Authority, the World Bank, the Hildebrand, L., and J. Sorensen. 2001. Draining the swamp World Conservation Union (IUCN), World Bank, Wash- and beating away the alligators: Baseline 2000. Intercoast ington, D.C., USA. Network: 20-21. Kenchington, R.A., and M.T. Agardy. 1990. Achieving ma- Hjort, J. 1914. Fluctuations in the great fisheries of northern rine conservation through biosphere reserve planning and Europe viewed in the light of biological research. Rap- management. Environmental Conservation 17(1): 39-44. ports et Proces-Verbaux Des Reunions, Conseil Interna- Kimball, L.A. 2001. International Ocean Governance. Using tional pour l’Exploration de la Mer 20:1-228. International Law and Organizations to Manage Resourc- Hughes, T.P., A.H. Baird, D.R. Bellwood, M. Card, S.R. Con- es Sustainably. IUCN, Gland, Switzerland and Cambridge, nolly, C. Folke, R.Grosberg, O. Hoegh-Guldberg, J.B.C. UK. Jackson, J. Kleypas, J.M. Lough, P. Marshall, M. Nystrom, Koenig, C.C., F.C. Coleman, L.A. Collins. Y. Sadovy, and P.L. S.R. Palumbi, J.M. Pandolfi, B. Rosen, and J. Roughgarden. Colin. 1996. Reproduction of gag (Mycteroperca micro- 2003. Climate change, human impacts, and the resilience lepis) (Pisces: Serranidae) in the eastern Gulf of Mexico of coral reefs. Science 301(5635): 929-933. and the consequences of fishing spawning aggregations. Intergovernmental Panel on Climate Change (IPCC). 2003. ICLARM Conf. Proc. Manila 48:307-323. Climate Change 2001. The Scientific Basis. Contribution Koslow, J.A., K. Gollett-Holmes, J.K. Lowry, T. O’Hara, of Working Group I to the Third Assessment Report. J.T. G.C.B. Poore, and A. Williams. 2001. Seamount benthic Houghton, Y. Ding, D.J. Griggs, M. Noguer, P.J. van der macrofauna off southern Tasmania: community structure Linden, X. Dai, K. Maskell, C.A. Johnson, eds. Published and impacts of trawling. Marine Ecology Progress Series for the Intergovernmental Panel on Climate Change, 213: 111-125. Cambridge University Press, Cambridge, UK. Kulczycki, G.R., R.W. Virnstein, and W.G. Nelson. 1981. The Isaksson, I., L. Phil, and J. van Montfrans. 1994. Eutrophi- relationship between fish abundance and algal biomass in cation-related changes in macro vegetation and foraging a seagrass-drift algae community. Estuarine Coastal Shelf of young cod (Gadus morhua.): a mesocosm experiment. Science 12: 341-347. Journal of Experimental Marine Biology and Ecology 177: Levin, L.A., D.F. Boesch, A. Covich, C. Dahm, C. Erseus, K.C. 203-217. Ewel, R.T. Kneib, A. Moldenke, M.A. Palmer, P. Snelgrove, Jackson, G.A., and R.R. Straghtmann. 1981. Larval mortality D. Strayer, and J.M. Weslawski. 2001. The function of ma- from offshore mixing as a link between precompetent and rine critical transition zones and the importance of sedi- competent periods of development. American Naturalist ment biodiversity. Ecosystems 4:430-451.

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS 38

Levin, L.A., D.J. DeMaster, L.D. McCann, and C.L. Thomas. D.C., USA. 1986. Effects of giant protozoan (Class Xenophyophorea) Moberg, F., and P. Ronnback. 2003. Ecosystem services of the on deep-seamount benthos. Marine Ecology Progress Se- tropical seascape: interactions, substitutions and restoration. ries 29:99-104. Ocean & Coastal Management 46(1-2): 27-46. Levitan, D.R. 1992. Community structure in times past: influ- Mumby, P.J., C.P. Dahlgren, A.R. Harborne, C.V. Kappel, F. ences of human fishing pressure on algal-urchin interac- Micheli, D.R. Brumbaugh, K.E. Holmes, J.M. Mendes, K. tions. Ecology 73: 1597-1605. Broad, J.M. Sanchirico, K. Buch, S. Box, R.W. Stoffle, and Lissner, A.L., G.L.Taghon, and D.R. Diener. 1991. Recolo- A.B. Gill. 2006. Fishing, trophic cascades, and the process of nization of deep-water hard-substrate communities: po- grazing on coral reefs. Science 311: 98-101. tential impacts from oil and gas development. Ecological Murray, S.N., J.A. Zertuche-Gonzalez, and L. Fernandez. Applications 1: 258-267. 2005. Invasive seaweeds: status of knowledge and eco- Liu, J.G., G.C. Daily, P.R. Ehrlich, and G.W. Luck. 2003. Ef- nomic policy considerations for the pacific coast of north fects of household dynamics on resource consumption and america. CEC, Montreal, Canada. biodiversity. Nature 421(6922): 530-533. Murray, S.N., T.J. Denis, J.S. Kido, and J.R. Smith. 1999. Hu- Longhurst, A. 1998. Ecological Geography of the Oceans. man visitation and the frequency and potential effects of Academic Press, SanDiego, CA, USA. collecting on rocky intertidal populations in southern Cal- Lubchenco, J. 1998. Entering the century of the environment: ifornia marine reserves. CalCOFI Rep. 40: 100-106. A new social contract for science. Science 279(5350): 491- National Oceanic and Atmospheric Administration. 2003. In- 497. vasive Marine Species found on Georges Bank. [online] Mann, K., and L. Lazier. 1991. Dynamics of Marine Systems. Cited November 2004. Available from http://www.no- Blackwell Scientific Publications, Boston, MA, USA. aanews.noaa.gov/stories2003/s2125.htm McGinn, A.P. 1999. Worldwatch Paper No. 145: Safeguarding National Research Council (NRC). 1992. Restoration of the Health of Oceans. Worldwatch Institute, Washington, Aquatic Systems: Science, Technology, and Public Policy. D.C., USA. National Academy Press, Washington, D.C., USA. McKee, J.K., P.W. Sciulli, C.D. Fooce, and T.A. Waite. 2004. National Research Council (NRC). 2001. Marine Protected Forecasting global biodiversity threats associated with Areas: Tools for Sustaining Ocean Ecosystem. National human population growth. Biological Conservation Academy Press, Washington, D.C., USA. 115(1):161-164. Norse, E. 1993. Marine Biological Diversity. Island Press, McKinney, M.L. 1998. Is marine biodiversity at less risk? Evi- Washington, D.C., USA. dence and implications. Diversity and Distributions 4(1): Nystrom, M., C. Folke, and F. Moberg. 2000. Coral reef dis- 3-8. turbance and resilience in a human-dominated environ- Millennium Ecosystem Assessment (MA). 2005a. Ecosystems ment. Trends in Ecology & Evolution 15(10): 413-417. and Human Well-Being: Biodiversity Synthesis Report. Ochieng, C.A., and P.L.A. Erftemeijer. 2003. The seagrasses WRI, Washington, D.C., USA. of Kenya and Tanzania. In: E.P. Green and F.T. Short, eds. Millennium Ecosystem Assessment (MA). 2005b. Millennium World Atlas of Seagrasses. University of California Press, Ecosystem Assessment. Vol. 1 Conditions and Trends. Ch. Berkeley, CA, USA. 19: Coastal Systems and Coastal Communities. Island Press, Odum, E., G.W. Barnett. 2004. Fundamentals of Ecology. Washington, D.C., USA. Saunders. Philadelphia, PA, USA. Millennium Ecosystem Assessment (MA). 2005c. Millennium Paine, R.T. 2002. Trophic control of production in a rocky Ecosystem Assessment. Vol. 1 Conditions and Trends. Ch. intertidal community. Science 296:736-739. 18: Marine Fisheries Systems. Island Press, Washington, Pauly, D., V. Christensen, J. Dalsgaard, R. Froese, and F. Torres

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS 39

Jr. 1998. Fishing down marine food webs. Science 279: Shaffer, H.B., R.N. Fisher, and C. Davidson. 1998. The role 860-863. of natural history collections in documenting species de- Pauly, D., V. Christensen, S. Guenette, T.J. Pitcher, U.R. Su- clines. Trends in Ecology and Evolution 13: 27-30. maila, C.J. Walters, R. Watson, and D. Zeller. 2002. Towards Sherman, K. 1993. Large Marine Ecosystems as Global Units sustainability in world fisheries. Nature 418(6898): 689- for Marine Resources Management: An Ecological Per- 695. spective. Pages 3-14 in K. Sherman, L.M. Alexander, and Rogers, S.I., M.I. Kaiser, and S. Jennings. 1998. Ecosystem B.D. Gold, editors. Large Marine Ecosystems: Stress, Miti- effects of demersal fishing: a European perspective. Pages gation, and Sustainability. American Association for the 68-78 in E.M. Dorsey, and J. Pederson, editors. Effects of Advancement of Science Press, Washington, D.C., USA. Fishing Gear on the Sea Floor of New England. Conser- Simson, S.D., M. Meekan J. Montgomery, R. McCauley, and vation Law Foundation, Boston, MA, USA. A. Jeffs. 2005. Homeward sound. Science 308:221. Rogers, A.D. 1999. The biology of Lophelia pertusa (Lin- Simenstad, C.A., S.B. Brandt, A. Chalmers, R. Dame, L.A. naeus 1758) and other deep-water corals and impacts from Deegan, R. Hodson, and E.D. Houde. 2000. Habitat-Bi- human activities. International Review of Hydrobiology otic Interactions. Pages 427-455 in J.E. Hobbie, editor. Es- 84 (4): 315-406. tuarine Science: A Synthetic Approach to Research and Ruiz, G.M., and J.A. Crooks. 2001. Biological invasions of Practice. Island Press, Washington, D.C., USA. marine ecosystems: patterns, effects, and management. Sinclair, M., and G. Valdimarsson. 2003. Responsible Fisheries Pages 1-17 in L. Bendell-Yound and P. Gallagher, editors. in the Marine Ecosystem. CABI Press, Cambridge, UK. Waters in Peril. Kluwer Academic Publications, Dordre- Sorensen, J. 1993. The International Proliferation of Integrat- cht, The Netherlands. ed Coastal Zone Management Efforts. Ocean & Coastal Ruiz, G.M., J.T. Carlton, E.D. Grosholz, and A.H. Hines. Management 21(1-3): 45-80. 1997. Global invasions of marine and estuarine habitats by Sorensen, J. 1997. National and international efforts at inte- non-indigenous species: Mechanisms, extent, and conse- grated coastal management: Definitions, achievements, and quences. American Zoologist 37(6): 621-632. lessons. Coastal Management 25(1): 3-41. Sala, E., and M.H. Graham. 2002. Community-wide distri- Sorensen, J. 2002. Baseline 2000 Background Report: The Sta- bution of predator-prey interaction strength in kelp for- tus of Integrated Coastal Management as an International ests. PNAS 99:3678-3683. Practice (Second Iteration). Cited November 2004. Avail- Sala, E., C.F. Boudouresque, and M. Harmelin-Vivien. 1998. able from http://www.uhi.umb.edu/b2k/baseline2000. Fishing, trophic cascades, and the structure of algal assem- pdf. blages: evaluation of an old but untested paradigm. Oikos Spalding, M.D., F. Blasco, and C.D. Field. 1997. World Man- 83: 425-439. grove Atlas. The International Society for Mangrove Eco- Sale, P.F., edditor. 1991. The Ecology of Fishes on Coral systems, Okinawa, Japan. Reefs. Academic Press, San Diego, CA, USA. Spalding, M., M. Taylor, C. Racilious, F. Short, E. Green. 2003. Sale, P.F., R.K. Cowen, B.S. Danilowicz, G.P. Jones, J.P. Kritzer, Global overview: the distribution and status of seagrasses. K.C. Lindeman, S. Planes, N.V.C. Polunin, G.R. Russ, Y.J. Pages 5-26 in E.P. Green, F.T. Short, editors. World Atlas of Sadovy, and R.S. Steneck. 2005. Critical science gaps im- Seagrasses: Present Status and Future Conservation. Uni- pede use of no-take reserves. Trends in Ecology and Evo- versity of California Press, Berkeley, CA, USA. lution 22(2). Steele, J. 1985. A comparison of terrestrial and marine sys- Sebens, K.P. 1986. Spatial relationships among encrusting tems. Nature 313:355-358. marine organisms in the New England subtidal zone. Steneck, R.S. 1998. Human influences on coastal ecosystems: Ecological Monographs 56: 73-96. Does overfishing create trophic cascades? Trends in Ecol-

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS 40

ogy and Evolution 13: 429-430. United Nations Publications, NY, USA. Tegner, M.J., L.V. Basch, and P.K. Dayton. 1996. Near extinction of an exploited marine invertebrate. Trends in Glossary Ecology and Evolution 11(7): 278-289. Tegner, M.J. and P.K. Dayton. 2000. Ecosystem effects of Allee effect: the relationship between high numbers of re- fishing on kelp forest communities. ICES Journal of Ma- producing adults and the successful subsequent recruitment rine Science 57:579-580. of young. Thrush, S. F., and P. K. Dayton. 2002. Disturbance to marine benthic habitats by trawling and dredging: implications for Anadromous: f�ish that hatch their rear in freshwater, migrate marine biodiversity. Annual Review of Ecology and Sys- to the ocean to grow and mature, and migrate back to fresh tematics 33. water to spawn. Tegner, M.J., P.K. Dayton. 1977. Sea urchin recruitment patterns and implications of commercial fishing. Science Anoxic: without oxygen. 196:324-326. Tomczak, M. 2000. Introduction to Physical Oceanography. Ballast water: water taken up or released by a ship to stabilize Available from http://gyre.umeoce.maine.edu/physi- it, or to raise/lower it in the water column. calocean/Tomczak/IntroOc/lecture11.html Turner, R.E., and N.N. Rabalais. 1994. Coastal eutrophica- Bathymetry: the measures of the depth of the ocean floor tion near the Mississippi River Delta. Nature 368: 619- from the water surface; the oceanic equivalent of topography. 621. UNEP. 1992. The World Environment 1972-1992: Two De- Benthos: the bed or bottom of a body of water, including the cades of Challenge. Chapman and Hall, NY, USA. layers of much silt, or sand. UNEP. 2002. Water supply and sanitation coverage in UNEP Regional Seas. UNEP, Nairobi. Biofouling: the formation of bacterial film (biofilm) on frag- Valiela, I., J.L. Bowen, and J.K. York. 2001. Mangrove forests: ile reverse osmosis membrane surfaces. One of the world’s most threatened major tropical environments. BioScience 51(10): 807-815. Biome: an entire community of living organisms in a single Vetter, E.W., and P.K. Dayton. 1998. Macrofaunal commu- major ecological area. nities within and adjacent to a detritus-rich submarine canyon system. Deep-Sea Research II 45:25-54. Biota: the animals, plants, and microbes that live in a particular Wang, H. 2004. Ecosystem management and its application to location or region. large marine ecosystems. Science, Law and Politics. Ocean development and international law 35(1): 41-74. Cnidarian: a coelenterate. Radially symmetrical animals hav- Witman, J.D., and K. Sebens. 1992. Regional variation in fish ing saclike bodies with only one opening and tentacles with predation intensity: a historical perspective of the Gulf of stinging structures. They occur in polyp or medusa forms. Maine. Oecologia 90:305-315. World Commission on Environment and Development. Coalesced: grown together, fused or joined together into a 1987. Our Common Future. Oxford University Press, whole. Melbourne, Australia. Zaitsev, I.P., and V.O. Mamaev. 1997. Marine Biological Di- Coastal zone: lands and waters adjacent to the coast that exert versity in the Black Sea: A Study of Change and Decline. an influence on the uses of the sea and its ecology, or whose

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS 41

uses and ecology are affected by the sea. fresh and salt water mix.

Continental shelf: a submerged border of a continent that Eutrophication: over-enrichment of a water body with nu- slopes gradually and extends to a point of steeper descent to trients, resulting in excessive growth of organisms and the the ocean bottom. depletion of the oxygen concentration.

Copepods: a common herbivorous zooplankton. Small crus- Extirpation: the elimination of a species or subspecies from a taceans found in either salt or fresh water. particular area, but not from its entire range.

Coriolis force: a force exerted on a parcel of air (or any mov- Fecund: species that have a high reproductive output based on ing body) due to the rotation of the earth. This force causes when and how often they reproduce. a deflection of the body to the right in the Northern hemisphere and to the left in the Southern hemisphere. Fiord: an estuary that occurs in a deep, narrow, drowned val- ley, originally formed by glaciers. Crustacean: aquatic arthropods that are characterized by a segmented body, chitinous exoskeleton, a pair of often modi- Flocculent layer: having a fluffy character or appearance. fied appendages on each segment, and two pairs of antennae. They include lobsters, shrimps, crabs, wood lice, water fleas, Foraminifera: a class of animals of very low organization and and barnacles. generally of small size, having a jelly-like body, a surface from which delicate filaments can be given off and retracted for Ctenophore: any of a phylum (Ctenophora) of marine ani- the prehension of external objects, and having a calcareous or mals superficially resembling jellyfishes but having biradial sandy shell, usually divided into chamber and perforated with symmetry and swimming by means of eight meridional small apertures. bands of transverse ciliated plates; also called comb jellies. Global commons: natural assets outside national jurisdiction Dredge: equipment for collecting and bringing up objects such as the ocean, outer space, and the Antarctic. from the seabed by dragging. Gyres: currents moving in large circles in the Northern and Echinoderm: a large group of animals characterized by five- Southern hemispheres. fold symmetry and a skeleton of calcite plates. Examples include starfish, urchins, and sea lilies. Intertidal: the zone between high and low tide.

Ecological footprint: a calculation that estimates the area of Keystone species: a species that plays a large or critical role Earth’s productive land and water required to supply the re- in supporting the integrity of its ecological community, and sources that an individual or group demands, as well as to whose removal leads to a series of extinctions within the eco- absorb the wastes that the individual or group produces. system.

Ecosystem engineer: any organism that creates or modifies Lagoon: a body of comparatively shallow salt water separated habitats. from the deeper sea by a shallow or exposed sandbank, coral reef, or similar feature. Estuary: the wide part of a river where it nears the sea, and

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS 42

Longshore current: current located in the surf zone and run- Phytoplankton: Microscopic floating plants, mainly algae that ning parallel to the shore as a result of waves breaking at live suspended in bodies of water and that drift about because angle on the shore. they cannot move by themselves or because they are too small or too weak to swim effectively against a current. Mangrove forest: an expanse of mangrove trees. Trees that live along the shore in tropical waters with their roots in the Propagule: any part of a plant that can give rise to a new in- salt water. dividual and aids in the dispersal of the species.

Marine protected area: an area of sea especially dedicated to Protist: a heterogeneous group of living things, comprising the protection and maintenance of biological diversity and those eukaryotes that are neither animals, plants, or fungi, or of natural and associated cultural resources, and managed unicellular, or colonial organisms. Includes most protozoa and through legal or other effective means. most algae.

Marine snow: aggregates of detritus, visible to the naked eye, Refugia: an area, untreated with pesticides, provided to pre- that consists of dead organisms, discarded feeding structures, serve susceptible populations of pests. fecal pellets, and other organic debris. Regime shift: a rapid modification of ecosystem organization Marsh: a low-lying wetland with grassy vegetation, usually a and dynamices with prolonged consequences. transition zone between land and water. Riparian: relating to or living or located on the bank of a Maximum sustainable yield: the largest average catch that can natural watercourse (as a river) or sometimes of a lake or tide- be taken continuously (sustained) from a stock under existing water. environmental conditions. Seiches: the oscillation of a body of water at its natural period. Meso-scale: the scale of meteorological phenomena that Coastal measurements of sea level often show seiches with ranges in size from a few kilometers to 200 kilometers in amplitudes of a few centimeters and periods of a few minutes horizontal extent, includes local winds, thunderstorms, and due to oscillations of the local harbor, estuary, or bay, super- tornadoes. imposed on the normal tidal changes.

Mollusk: an invertebrate animal with soft, unsegmented bod- Spawn: the act of reproduction of fishes. ies, such as clams and snails, usually enclosed in a calcium shell. Sponge: a poriferan. Primitive, sessile, mostly marine, water dwelling filter feeders that pump water through their matrix Pelagic: fish and animals that live in the open sea, away from to filter out particulates of food matter. the sea bottom. Stratification: the division into distinct layers (or strata). Photic zone: the layer of the ocean that is penetrated by sun- light, extending to a depth of about 200 meters. Thermocline: a vertical negative teperature gradient in some layer of a body of water that is appreciably greater than the Phyletic diversity: of or relating to the diversity of the evolu- gradients above and below this level. tionary development of organisms.

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc SYNTHESIS 43

Thermohaline: the circulation path determined by tempera- Upwelling: vertical currents that deliver cold, nutrient-rich ture and salt, downwellings due to surface-water density cre- bottom waters to the surface. ated by low temperature and high salinity. Zooplankton: small, usually microscopic animals (such as pro- Trawl: a string of traps or nets connected by a line with two tozoans) that drift with the currents. May be either herbivores buoys marking each end that are dragged along the bottom or carnivores. to catch fish or towed at various depths above the bottom for the same purpose.

Introduction to Marine Conservation Biology Lessons in Conservation http://ncep.amnh.org/linc